Sample Interview Questions – Technical Stream

Sample Question on Engineering
Electrical Engineering
  1. How grounding is different than earthings?
  2. What is diversity factor in electric installations?
  3. Explain Marx circuit.
  4. Why human body feel electric shock?
  5. What is the principal of motor?
  6. What is power factor?
  7. Should power factor be low or high?
  8. Difference between field rheostat and armature rheostat.
  9. Why field rheostat is kept in minimum position?
  10. Why armature rheostat is kept in maximum position?
  11. What is meant by derating factor?
  12. What is stiffness factor?
  13. What is the dependency of stiffness on load angle?
  14. What is 100% protection of generator? Why 100% is not used but 95% is generally used?
  15. What is the difference between a Verilog task and Verilog function?.
  16. What is the unit of magnetic flux density? .
  17. Why increase in current leads to increase in conductor temperature?
  18. How can a equal potential zone be carried out in conductors?
  19. What is essential to prove safe isolation of electrical circuit?
  20. What is the ratio of true power to apparent power in an AC circuit?
  21. What is power relay? 22. Differentiate between power relay and reverse power relay.
  22. What is the suitable transmission voltage?
  23. What is the maximum operating temperature for a thermoplastic insulated cable?
  24. Explain the working of variable frequency transformer?
  25. Which oil can be used in transformer?
  26. What is excitation in case of DC motor?
  27. Why is the starting current high in DC motor?
  28. What is rotary phase converter?
  29. Differentiate between digital phase converter and ordinary phase converter.
  30. What is knee point voltage?
  31. List the advantages of star-delta starter with induction motor?
  32. Which type of transformer is used for lighting loads?
  33. What is star-delta transformer?
  34. Why star delta starter is preferred with induction motor?
Star delta starter is preferred with induction motor due to following reasons: • Starting current is reduced 3-4 times of the direct current due to which voltage drops and hence it causes less losses. • Star delta starter circuit comes in circuit first during starting of motor, which reduces voltage 3 times, that is why current also reduces up to 3 times and hence less motor burning is caused. • In addition, starting torque is increased and it prevents the damage of motor winding.
35. State the difference between generator and alternator
Generator and alternator are two devices, which converts mechanical energy into electrical energy. Both have the same principle of electromagnetic induction, the only difference is that their construction. Generator persists stationary magnetic field and rotating conductor which rolls on the armature with slip rings and brushes riding against each other, hence it converts the induced emf into dc current for external load whereas an alternator has a stationary armature and rotating magnetic field for high voltages but for low voltage output rotating armature and stationary magnetic field is used.
36. Why AC systems are preferred over DC systems?
Due to following reasons, AC systems are preferred over DC systems: a. It is easy to maintain and change the voltage of AC electricity for transmission and distribution. b. Plant cost for AC transmission (circuit breakers, transformers etc) is much lower than the equivalent DC transmission c. From power stations, AC is produced so it is better to use AC then DC instead of converting it. d. When a large fault occurs in a network, it is easier to interrupt in an AC system, as the sine wave current will naturally tend to zero at some point making the current easier to interrupt.
37. How can you relate power engineering with electrical engineering?
Power engineering is a sub division of electrical engineering. It deals with generation, transmission and distribution of energy in electrical form. Design of all power equipments also comes under power engineering. Power engineers may work on the design and maintenance of the power grid i.e. called on grid systems and they might work on off grid systems that are not connected to the system.
38. What are the various kind of cables used for transmission?
Cables, which are used for transmitting power, can be categorized in three forms: • Low-tension cables, which can transmit voltage upto 1000 volts. • High-tension cables can transmit voltage upto 23000 volts. • Super tension cables can transmit voltage 66 kV to 132 kV.
39. Why back emf used for a dc motor? highlight its significance.
The induced emf developed when the rotating conductors of the armature between the poles of magnet, in a DC motor, cut the magnetic flux, opposes the current flowing through the conductor, when the armature rotates, is called back emf. Its value depends upon the speed of rotation of the armature conductors. In starting, the value of back emf is zero.
40. What is slip in an induction motor?
Slip can be defined as the difference between the flux speed (Ns) and the rotor speed (N). Speed of the rotor of an induction motor is always less than its synchronous speed. It is usually expressed as a percentage of synchronous speed (Ns) and represented by the symbol ‘S’.
41. Explain the application of storage batteries.
Storage batteries are used for various purposes, some of the applications are mentioned below:
  • For the operation of protective devices and for emergency lighting at generating stations and substations. • For starting, ignition and lighting of automobiles, aircrafts etc. • For lighting on steam and diesel railways trains. • As a supply power source in telephone exchange, laboratories and broad casting stations. • For emergency lighting at hospitals, banks, rural areas where electricity supplies are not possible.
9. Explain advantages of storage batteries
Few advantages of storage batteries are mentioned below: • Most efficient form of storing energy portably. • Stored energy is available immediately because there is no lag of time for delivering the stored energy. • Reliable source for supply of energy. • The energy can be drawn at a fairly constant rate.
10. What are the different methods for the starting of a synchronous motor.
Starting methods: Synchronous motor can be started by the following two methods: • By means of an auxiliary motor: The rotor of a synchronous motor is rotated by auxiliary motor. Then rotor poles are excited due to which the rotor field is locked with the stator-revolving field and continuous rotation is obtained. • By providing damper winding: Here, bar conductors are embedded in the outer periphery of the rotor poles and are short-circuited with the short-circuiting rings at both sides. The machine is started as a squirrel cage induction motor first. When it picks up speed, excitation is given to the rotor and the rotor starts rotating continuously as the rotor field is locked with stator revolving field.
11. Name the types of motors used in vacuum cleaners, phonographic appliances, vending machines, refrigerators, rolling mills, lathes, power factor improvement and cranes.
Following motors are used: – • Vacuum cleaners- Universal motor. • Phonographic appliances – Hysteresis motor. • Vending machines – Shaded pole motor. • Refrigerators – Capacitor split phase motors. • Rolling mills – Cumulative motors. • Lathes – DC shunt motors. • Power factor improvement – Synchronous motors.
12. State Thevenin’s Theorem:
According to thevenin’s theorem, the current flowing through a load resistance  Connected across any two terminals of a linear active bilateral network is the ratio open circuit voltage (i.e. the voltage across the two terminals when RL is removed) and sum of load resistance and internal resistance of the network. It is given by Voc / (Ri + RL).
13. State Norton’s Theorem
The Norton’s theorem explains the fact that there are two terminals and they are as follows: • One is terminal active network containing voltage sources  • Another is the resistance that is viewed from the output terminals. The output terminals are equivalent to the constant source of current and it allows giving the parallel resistance.  The Norton’s theorem also explains about the constant current that is equal to the current of the short circuit placed across the terminals. The parallel resistance of the network can be viewed from the open circuit terminals when all the voltage and current sources are removed and replaced by the internal resistance.
14. State Maximum power transfer theorem
The Maximum power transfer theorem explains about the load that a resistance will extract from the network. This includes the maximum power from the network and in this case the load resistance is being is equal to the resistance of the network and it also allows the resistance to be equal to the resistance of the network. This resistance can be viewed by the output terminals and the energy sources can be removed by leaving the internal resistance behind.
15. Explain different losses in a transformer.
There are two types of losses occurring in transformer: • Constant losses or Iron losses: The losses that occur in the core are known as core losses or iron losses. Two types of iron losses are: o eddy current loss  o Hysteresis loss.  These losses depend upon the supply voltage, frequency, core material and its construction. As long as supply voltage and frequency is constant, these losses remain the same whether the transformer is loaded or not. These are also known as constant losses. • Variable losses or copper losses: when the transformer is loaded, current flows in primary and secondary windings, there is loss of electrical energy due to the resistance of the primary winding, and secondary winding and they are called variable losses. These losses depend upon the loading conditions of the transformers. Therefore, these losses are also called as variable losses.
16. Explain different types of D.C motors? Give their applications
Different type of DC motors and their applications are as follows:- • Shunt motors: It has a constant speed though its starting torque is not very high. Therefore, it is suitable for constant speed drive, where high starting torque is not required such as pumps, blowers, fan, lathe machines, tools, belt or chain conveyor etc. • Service motors: It has high starting torque & its speed is inversely proportional to the loading conditions i.e. when lightly loaded, the speed is high and when heavily loaded, it is low. Therefore, motor is used in lifts, cranes, traction work, coal loader and coal cutter in coalmines etc. • Compound motors: It also has high starting torque and variable speed. Its advantage is, it can run at NIL loads without any danger. This motor will therefore find its application in loads having high inertia load or requiring high intermittent torque such as elevators, conveyor, rolling mill, planes, presses, shears and punches, coal cutter and winding machines etc.
17. Explain the process of commutation in a dc machine. Explain what are inter-poles and why they are required in a dc machine.
Commutation: It is phenomenon when an armature coil moves under the influence of one pole- pair; it carries constant current in one direction. As the coil moves into the influence of the next pole- pair, the current in it must reverse. This reversal of current in a coil is called commutation. Several coils undergo commutation simultaneously. The reversal of current is opposed by the static coil emf and therefore must be aided in some fashion for smooth current reversal, which otherwise would result in sparking at the brushes. The aiding emf is dynamically induced into the coils undergoing commutation by means of compoles or interpoles, which are series excited by the armature current. These are located in the interpolar region of the main poles and therefore influence the armature coils only when these undergo commutation.
18. Comment on the working principle of operation of a single-phase transformer.
Working principle of operation of a single-phase transformer can be explained as An AC supply passes through the primary winding, a current will start flowing in the primary winding. As a result, the flux is set. This flux is linked with primary and secondary windings. Hence, voltage is induced in both the windings. Now, when the load is connected to the secondary side, the current will start flowing in the load in the secondary winding, resulting in the flow of additional current in the secondary winding. Hence, according to Faraday’s laws of electromagnetic induction, emf will be induced in both the windings. The voltage induced in the primary winding is due to its self inductance and known as self induced emf and according to Lenze’s law it will oppose the cause i.e. supply voltage hence called as back emf. The voltage induced in secondary coil is known as mutually induced voltage. Hence, transformer works on the principle of electromagnetic induction.
19. Define the following terms:-
• Reliability, • Maximum demand, • Reserve-generating capacity,  • Availability (operational).
Reliability: It is the capacity of the power system to serve all power demands without failure over long periods. Maximum Demand: It is maximum load demand required in a power station during a given period. Reserve generating capacity: Extra generation capacity installed to meet the need of scheduled downtimes for preventive maintenance is called reserve-generating capacity. Availability: As the percentage of the time a unit is available to produce power whether needed by the system or not.
20. Mention the disadvantages of low power factor? How can it be improved?
Disadvantages of low power factor: • Line losses are 1.57 times unity power factor. • Larger generators and transformers are required. • Low lagging power factor causes a large voltage drop, hence extra regulation equipment is required to keep voltage drop within prescribed limits. • Greater conductor size: To transmit or distribute a fixed amount of power at fixed voltage, the conductors will have to carry more current at low power factor. This requires a large conductor size.
21. State the methods of improving power factor?
Methods of improving power factor: • By connecting static capacitors in parallel with the load operating at lagging power factor.  • A synchronous motor takes a leading current when over excited and therefore behaves like a capacitor. • By using phase advancers to improve the power factor of induction motors. It provides exciting ampere turns to the rotor circuit of the motor. By providing more ampere-turns than required, the induction motor can be made to operate on leading power factor like an overexcited synchronous motor.
22. State the factors, for the choice of electrical system for an aero turbine.
The choice of electrical system for an aero turbine is guided by three factors: • Type of electrical output: dc, variable- frequency ac, and constant- frequency ac. • Aero turbine rotational speed: constant speed with variable blade pitch, nearly constant speed with simpler pitch- changing mechanism or variable speed with fixed pitch blades. • Utilization of electrical energy output: in conjunction with battery or other form of storage, or interconnection with power grid.
23. What are the advantages of VSCF wind electrical system?
Advantages of VSCF wind electrical system are: • No complex pitch changing mechanism is needed. • Aero turbine always operates at maximum efficiency point. • Extra energy in the high wind speed region of the speed – duration curve can be extracted • Significant reduction in aerodynamic stresses, which are associated with constant – speed operation.
24. Explain the terms real power, apparent power and reactive power for ac circuits and also the units used.
  • Real Power: It is the product of voltage, current and power factor i.e. P = V I cos j and basic unit of real power is watt. i.e. Expressed as W or kW. • Apparent power: It is the product of voltage and current. Apparent power = V I and basic unit of apparent power is volt- ampere. Expressed as VA or KVA. • Reactive Power: It is the product of voltage, current and sine of angle between the voltage and current i.e. Reactive power = voltage X current X sinj or Reactive power = V I sin j and has no other unit but expressed in VAR or KVAR.
25. Define the following: Average demand, Maximum demand, Demand factor, Load factor.
  • Average Demand: the average power requirement during some specified period of time of considerable duration is called the average demand of installation. • Maximum Demand: The maximum demand of an installation is defined as the greatest of all the demand, which have occurred during a given period. It is measured accordingly to specifications, over a prescribed time interval during a certain period. • Demand Factor: It is defined as the ratio of actual maximum demand made by the load to the rating of the connected load. • Load Factor: It is defined as the ratio of the average power to the maximum demand.
26. Explain forward resistance, static resistance and dynamic resistance of a pn junction diode.
  • Forward Resistance: Resistance offered in a diode circuit, when it is forward biased, is called forward-resistance. • DC or Static Resistance: DC resistance can be explained as the ratio of the dc-voltage across the diode to the direct current flowing through it. • AC or Dynamic Resistance: It can be defined as the reciprocal of the slope of the forward characteristic of the diode. It is the resistance offered by a diode to the changing forward current.
27. How does Zener phenomenon differ from Avalanche breakdown?
The phenomenon when the depletion region expands and the potential barrier increases leading to a very high electric field across the junction, due to which suddenly the reverse current increases under a very high reverse voltage is called Zener effect. Zener-breakdown or Avalanche breakdown may occur independently or both of these may occur simultaneously. Diode junctions that breakdown below 5v are caused by Zener Effect. Junctions that experience breakdown above 5v are caused by avalanche-effect. The Zener-breakdown occurs in heavily doped junctions, which produce narrow depletion layers. The avalanche breakdown occurs in lightly doped junctions, which produce wide depletion layers.
28. Compare JFET’s and MOSFET’s.
Comparison of JFET’s and MOSFET’s: • JFET’s can only be operated in the depletion mode whereas MOSFET’s can be operated in either depletion or in enhancement mode. In a JFET, if the gate is forward-biased, excess-carrier injunction occurs and the gate-current is substantial. • MOSFET’s have input impedance much higher than that of JFET’s. Thus is due to negligible small leakage current. • JFET’s have characteristic curves more flat than that of MOSFET is indicating a higher drain resistance. • When JFET is operated with a reverse-bias on the junction, the gate-current IG is larger than it would be in a comparable MOSFET.
30. Explain thin film resistors and wire-wound resistors
  1. Thin film resistors- It is constructed as a thin film of resistive material is deposited on an insulating substrate. Desired results are obtained by either trimming the layer thickness or by cutting helical grooves of suitable pitch along its length. During this process, the value of the resistance is monitored closely and cutting of grooves is stopped as soon as the desired value of resistance is obtained. b. Wire wound resistors – length of wire wound around an insulating cylindrical core are known as wire wound resistors. These wires are made of materials such as Constantan and Manganin because of their high resistivity, and low temperature coefficients. The complete wire wound resistor is coated with an insulating material such as baked enamel
31. What is a differential amplifier? Also, explain CMRR.
Differential Amplifier: The amplifier, which is used to amplify the voltage difference between two input-lines neither of which is grounded, is called differential amplifier. This reduces the amount of noise injected into the amplifier, because any noise appearing simultaneously on both the input-terminals as the amplifying circuitry rejects it being a common mode signal. CMRR: It can be defined as the ratio of differential voltage-gain to common made voltage gain. If a differential amplifier is perfect, CMRR would be infinite because in that case common mode voltage gain would be zero.
Mechanical Engineering interview questions and answers
What is mechanism?
A mechanism is an assembly of different parts which perform a complete motion and is often part of a machine.
State Newton’s three laws of Motion.
– The law of inertia: Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it. – Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object). Force=Mass times acceleration. – For every action there is an equal and opposite reaction.
State the laws of thermodynamics and its importance of in Mechanical Engineering.
Thermodynamics is a physical science which studies the interrelation between heat, work and the internal energy of any system. Thermodynamics helps study all the systems of mechanical engineering. There are three laws of thermodynamics.
First Law: Energy can be neither created nor destroyed. It can only change forms. In any process in an isolated system, the total energy remains the same.
Eg: turning on a light would seem to produce energy; however, it is electrical energy that is converted.
Second Law: The second law of thermodynamics states that the entropy of any isolated system not in thermal equilibrium almost always increases.
Eg: A car that has run out of gas will not run again until you walk 10 miles to a gas station and refuel the car.
Third Law: As temperature approaches absolute zero, the entropy of a system approaches a minimum.
Eg: Water in gas form has molecules that can move around very freely. Water vapor has very high entropy (randomness). As the gas cools, it becomes liquid which can still move around but not as freely. At this point they have lost some entropy. On cooling further it becomes solid ice where molecules can no longer move freely but can only vibrate within the ice crystals. The entropy is now very low. As the water nears absolute zero, the vibration of the molecules diminishes. If the solid water reaches absolute zero, all molecular motion would stop completely. And at this point the water would have no entropy at all.
What is Hess law?
According to the Hess law the energy transfer is simply independent of the way being followed. If the reactant and the product of the whole process are the same then same amount of energy will be dissipated or absorbed.
What is PS?
Personal Statement. It is something that gives an informative background about an individual.
What is a bearing? What are the different types of bearings?
Bearing is a device that helps smoother movement with minimal friction which in turn helps enhances efficiency and speed. Considering two types of loading, radial and thrust, there are different types of bearings which help handle these loads. The basic difference in the types of loads is essentially due to their ability to handle weight and different kinds of loads for various applications. Different types of bearings are:
-Ball bearing -Roller bearing -Ball Thrust bearing -Roller thrust bearing -Tapered roller bearing -Magnetic bearings -Giant Roller Bearing
What is a process flow diagram?
A Process Flow Diagram is a user friendly, simplified sketch which illustrates general plant streams, major equipments and key central loops and shows the relationship between major components in the system. By using symbols to identify instruments and vessels it describes the primary flow course. They also provide e detail of mass/energy balance data along with stream composition and physical properties, however do not show minor components.
What is a time and motion theory?
Frederick Taylor was pioneer of the time and motion theory. This technique monitors the amount of time required to complete a task along with observing the steps taken by a worker to complete the given task.
Which is the hardest material on earth?
Diamond is currently the hardest material, made up of carbon atoms which cannot move. Carbon is the only atom that can have four electrons in the second shell surrounding the carbon nucleus, precisely why making a diamond the hardest material. However, there also are claims by a few to a new rare material called Wurtzite Boron Nitride which has a structure similar to a diamond but has some other atoms in place of carbon.
One unit of BTU is how many Joules?
1 BTU=1055.06 Joules
What does a pump develop? Give reason to support your answer.
Pump is a device that is used to transfer fluid from one place to another place which means it develops flow not pressure.
Explain the difference between pipe and a tube.
A pipe is measured based on its inner diameter (ID) whereas a tube is measured based on the outer diameter (OD). Other than the dimensions there is no major difference between the two.
Explain the formula of heat loss in a pipe.
In order to find total heat loss through the pipes it is imperative to know the thermal conductivity and the differing thicknesses of each layer. The ground that surrounds the pipe also acts as a layer of insulation. Considering this, the thermal properties of the stoneless sand is included in the heat loss calculation.
What kind of pipes are used for steam lines?
Pressure and temperature are two of the most important factors to be considered before selecting the type of material to be used. Steam is a compressible gas due to which the capacity of the pipe line depends on the size of the pipes and pressure of the steam. Since steam at even low pressure can be dangerous, extra care is to be taken. Galvanized pipes are usually not used for steam. Pipes made of mild steel with welded fittings are instead largely used.
Who invented the four stroke engine? According to you which one is more efficient, four stroke engine or a two stroke engine and why?
Nikolaus Otto invented the four stroke engine. Both, two stroke and four stroke have their own advantages and disadvantages. 4 stroke is more fuel efficient. However, 2 stroke produces more power.
What do you understand by the concept of a 6 stroke engine? Explain how it works.
The six stroke engine is based on the concept of four stroke engine but built with an intention of improvising the efficiency in reducing emission. Every cycle of a four stroke engine involves the upward and downward movement of the piston which happens twice in the chamber, resulting in four total strokes and one of which is the power stroke which provides the torque to move the vehicle. A six stroke engine works similarly except that there are two power strokes.
Explain what is torque
Torque is the force that causes rotation. It is a measure of how much force is acting on an object making it rotate.
What is the difference between torque and power?
While power determines the speed of a vehicle, torque determines the time in which that speed can be reached. The greater the torque figure, the faster the acceleration. The more torque in the engine, the faster you accelerate. Power is the rate at which work is done, so it is basically the potential of the engine.
Explain why diesel engine is known as high torque and petrol engine as high speed engine?
Each power stroke in a petrol engine releases more heat and is converted into mechanical energy due to a higher rate of burning. This is the reason petrol engine has higher power and acceleration.
Diesel engine is a compression ignition engine with higher compression ratio, therefore extreme pressure is high. Since the piston of a diesel engine is larger, more torque is delivered in produced.
Why do heavy vehicles use diesel engine?
The compression ratio of diesel engine is higher than the petrol engine, the reason for producing higher torque. The efficiency of diesel engine increases with load. Diesel produces slow energy on burning of fuel and the efficiency of the engine increases with load which is why diesel engine is suitable and largely used for heavy vehicles.
Explain the difference between projectile motion and rocket motion.
The major difference is that a projectile has no motor or a rocket on it, due to which the momentum is given to it as it is launched. A pen thrown across a room is a classic example of a projectile motion. On the other hand, a rocket or missile has a motor on it which helps in accelerating while moving. This helps in resisting other forces such as gravity. A projectile does not have any specific shape, it is a point mass, whereas rocket has a particular shape having its center of gravity situated at a particular point on its body. Thus rocket motion comes under kinetics and projectile comes under kinematics.
Between steel, copper and brass, which conduct faster heat.
Copper conducts heat faster than steel or brass. In most cases, material that is good for conducting heat is also good for electricity.
Explain the types of sensors.
(i) Temperature Sensor- This device collects information about the temperature from a source and converts it to a form which is understandable by another device or person. Glass thermometer is the best example where mercury acts as the temperature sensor.
(ii) IR Sensors- This device detects and/or emits infrared radiation to sense a particular phase in the environment. Mostly thermal radiation is emitted by all the objects in the infrared spectrum. This type of radiation is not visible to the human eye but the infrared sensor detects it.
(iii) UV Sensors- These sensors measure the intensity of the ultraviolet radiation. This form of electromagnetic radiation has wavelengths which are longer than x-rays yet shorter than visible radiation. UV sensors can discover the exposure of environment to ultraviolet radiation.
(iV) Touch Sensor- A touch sensor acts as a variable resistor based on the location where it is sensed. Proximity Sensor- A proximity sensor detects the presence of objects that are placed in close proximity without any point of contact.
What minerals are used in the manufacture of cars?
Cars are made from many various minerals. The steel body is made from the iron-rich minerals like magnetite and hematite. Door handles and badges are often coated in chromium which comes from chromite. Some of the other minerals used are aluminum, quartz, copper, magnesium, zinc, tin etc.
Which instrument measures speed in a car?
A speedometer helps measure the speed in the car.
What are the advantage and disadvantage of using LPG in a car?
The high octane rate enables it to blend better with air and to burn completely, generating less carbon. With less carbon buildup, spark plugs often last longer and oil changes are needed less frequently.
Since it burns in the gaseous phase, it results in less corrosion and engine wear.
In case of a spill, LPG evaporates quickly.
The LPG requires servicing at approximately once a year.
Since complete combustion occurs, more heat is liberated which is not advised for a long journey as the engine will get over heated.
Installation of LPG is rather difficult.
Why gas containers are mostly in a cylindrical shape?
The ideal shape would be a sphere. The container must have the capacity to withstand the extremely high pressure of liquefied gas. A spherical shape helps in distributing these forces uniformly.
Explain why re-heater is used in gas turbine
The advantage of reheater is that it significantly increases the thrust; which is a prime reason for its use in gas turbines.
How many types of suspensions are used in automobiles?
McPherson struts Leaf spring Coil spring Torsion beam Wishbone Air Suspension
What is DTSI? Why it is used in motor bikes?
Digital Twin Spark Ignition. This is used for a better fuel combustion in the cylinder head which helps provide better efficiency and optimum use of fuel.
What are the advantages of DTSI over normal engines?
The cylinder head has two spark plugs, instead of the usual one. When two sparks are generated at either ends of the combustion chamber, the air-fuel mixture is ignited in a way that creates two flame fronts. A higher rate of combustion is achieved leading to higher rise in pressure. The outcome of this is more torque, better fuel efficiency and lower emissions.
What is meant by gear ratio?
A gear ratio is a direct measure of ratio of the rotational speeds of two or more interlocking gears.
What is the ratio of specific heat of air?
The ratio of specific heat γ=CP/CV is a factor in adiabatic engine processes and in determining the speed of sound in gas. This ratio γ=1.66 for an ideal monoatomic gas and γ=1.4 for air, which is predominantly a diatomic gas.
What is the percentage of carbon present in pig iron?
Carbon content is generally 3.5-4.5%.
 What are the different types of fits? Explain?
On the basis of Indian standards fits can mainly be categorized into three groups: > Clearance Fit: These types of fits are characterized by the occurrence of a clearance between the two mating parts. The difference between the minimum size of the hole and the maximum size of the shaft is called the minimum clearance, the difference between the maximum size of the hole and the minimum size of the shaft is known as maximum clearance. > Interference Fit: In these types of fits the size of the mating parts are predefined so that interference between them always occurs. The tolerance zone of the hole is completely below the tolerance zone of the shaft. > Transition Fit: As the name suggests these type of fit has its mating parts sized limited to allow either clearance or interference. The tolerance zone of the hole and the shaft overlaps in case of such fits.
For a shaft designated as 40 H8/f7, calculate the tolerances.
Given: Shaft designation = 40 H8/f7 The shaft designation 40 H8/f 7 means that the basic size is 40 mm and the tolerance grade for the hole is 8 ( i. e. I T 8) and for the shaft is 7 ( i. e. I T 7). Since 40 mm lies in the diameter steps of 30 to 50 mm, therefore the geometric mean diameter, D = Square root of (30 x 50) = 38.73 mm We know that standard tolerance unit, i = 0.45 x Cube root of (D) + 0.001 D i = 0.45 × 3.38 + 0.03873 = 1.559 73 or 1.56 microns i = 1.56 × 0.001 = 0.001 56 mm …(1 micron = 0.001 mm) The standard tolerance for the hole of grade 8 (IT8) = 25 i = 25 × 0.001 56 = 0.039 mm  The standard tolerance for the shaft of grade 7 (IT7) = 16 i = 16 × 0.001 56 = 0.025 mm
What are the factors that can affect the Factor of safety selection?
The factor of safety is used in designing a machine component. Prior to selecting the correct factor of safety certain points must be taken into consideration such as: > The properties of the material used for the machine and the changes in its intrinsic properties over the time period of service. > The accuracy and authenticity of test results to the actual machine parts. > The applied load reliability. > The limit of stresses (localized). > The loss of property and life in case of failures. > The limit of initial stresses at the time period of manufacture. > The extent to which the assumptions can be simplified. The factor of safety also depends on numerous other considerations such as the material, the method of manufacturing , the various types of stress, the part shapes etc.
What is heat treatment and why is it done?
Heat treatment can be defined as a combination of processes or operations in which the heating and cooling of a metal or alloy is done in order to obtain desirable characteristics without changing the compositions. Some of the motives or purpose of heat treatment are as follows: > In order to improve the hardness of metals. > For the softening of the metal. > In order to improve the machinability of the metal. > To change the grain size. > To provide better resistance to heat, corrosion, wear etc.
Heat treatment is generally performed in the following ways: > Normalizing > Annealing > Spheroidising > Hardening > Tempering > Surface or case hardening
What are the rules that must be kept in mind while designing castings?
Some of the points that must be kept in mind during the process of cast designing are as follows: > To avoid the concentration of stresses sharp corners and frequent use of fillets should be avoided. > Section thicknesses should be uniform as much as possible. For variations it must be done gradually. > Abrupt changes in the thickness should be avoided at all costs. > Simplicity is the key, the casting should be designed as simple as possible. > It is difficult to create true large spaces and henceforth large flat surfaces must be avoided. > Webs and ribs used for stiffening in castings should as minimal as possible. > Curved shapes can be used in order to improve the stress handling of the cast.
What are the points that should be kept in mind during forging design?
Some of the points that should be followed while forging design are: > A radial flow of grains or fibers must be achieved in the forged components. > The forged items such as drop and press forgings should have a parting line that should divide the forging into two equal halves. > The ribs in a forging should not be high or thin. > In order to avoid increased die wear the pockets and recesses in forgings should be minimum. > In forgings the parting line of it should lie as far as possible in a single plane. > For ease of forging and easy removal of forgings the surfaces of the metal should contain sufficient drafts.
Describe briefly the different cold drawing processes.
Some of the important cold drawing processes are as follows: > Bar and Rod Drawing: In the case of bar drawing the hot drawn bars are at first pickled, washed and coated to prevent oxidation. Once this is done a draw bench is used for the process of cold drawing. In order to make an end possible to enter a drawing die the diameter of the rod is reduced by the swaging operation. This end is fastened by chains to the draw bench and the end is gripped by the jaws of the carriage. In this method a high surface finish and accuracy dimensionally is obtained. The products of this process can be used directly without any further machining. > Wire Drawing: Similar to the above process the bars are first pickled, washed and coated to prevent any oxidation. After this the rods are passed through several dies of decreasing diameter to provide a desired reduction in the size ( diameter ). The dies used for the reduction process is generally made up of carbide materials. >Tube Drawing: This type of drawing is very similar to the bar drawing process and in majority of cases it is accomplished by the use of a draw bench.
What are the different theories of failure under static load, explain briefly?
The main theories of failure of a member subjected to bi-axial stress are as follows: > Maximum principal stress theory ( Rankine’s theory): This theory states that failure occurs at a point in member where the maximum principal or normal stress in a bi-axial system reaches the maximum strength in a simple tension test. > Maximum shear stress theory ( Guest’s or Tresca’s theory): This theory states that failure occurs when the biaxial stress reaches a value equal to the shear stress at yield point in a simple tension test. > Maximum principal strain theory ( Saint Venant theory): This theory states that failure occurs when bi-axial stress reaches the limiting value of strain. > Maximum strain energy theory ( Haigh’s theory): This theory states that failure occurs when strain energy per unit volume of the stress system reaches the limiting strain energy point. > Maximum distortion energy theory ( Hencky and Von Mises theory): This theory states that failure occurs when strain energy per unit volume reaches the limiting distortion energy.
What are the assumptions made in simple theory of bending?
The assumptions made in the theory of simple bending are: > The material of the beam is homogeneous this implies that it is uniform in density, strength and have isotropic properties meaning possessing same elastic property in all directions. > Even after bending the cross section of the beam remains constant. > During the initial stages the beam is straight and unstressed. > All the stresses in the beam are within the elastic limit of its material. > The layers of the beam are free to contract and expand longitudinally and laterally > On any cross section the perpendicular resultant force of the beam is zero. > Compared to the cross-sectional dimension of the beam the radius of curvature is very large.
Why is stress considered important in a shaft?
The following types of stresses are prevalent in shafts: > At the outermost surface of the shaft the max shear stress occurs on the cross-section of the shaft. > At the surface of the shaft on the longitudinal planes through the axis of the shaft the maximum longitudinal shear stress occurs. > At 45 degrees to the maximum shearing stress planes at the surface of the shafts the major principal stress occurs. It equals the max shear stress on the cross section of the shaft. > For certain materials where the tensile and compressive strengths are lower in measure as compared to the shear strength, then the shaft designing should be carried out for the lowest strengths.  > All these stresses are of significance as they play a role in governing the failure of the shaft. All theses stresses get generated simultaneously and hence should be considered for designing purposes
 What do you understand by the Hooke`s Coupling what are its purposes?
The Hooke`s coupling is used to connect two shafts whose axes intersect at a small angle. The two shafts are inclined at an angle and is constant. During motion it varies as the movement is transferred from one shaft to another. One of the major areas of application of this coupling is in gear boxes where the coupling is used to drive the rear wheels of trucks and other vehicles. In such usage scenarios two couplings are used each at the two ends of the coupling shaft. they are also used to transfer power for multiple drilling machines. The Hooke`s coupling is also known as the Universal coupling. The torque transmitted by the shafts is given by : T= (pie/16) x t x (d) cube Where T = torque, t = shear stress for the shaft material and d the diameter of the shaft.
 What kind of materials should be used for shafts manufacturing?
Some of the qualities that should be present in materials for shafts are as follows:
The material should have a high index of strength.
Also it should have a high level of machinability.
The material should possess a low notch sensitivity factor.
The material must also have wear resistant properties.
 Good heat treatment properties should also be present
The common material used to creates shafts of high strengths an alloy of steel like nickel is used. The shafts are manufactured by hot rolling processes and then the shaft is finished using drawing or grinding processes.
Why should a chain drive be used over a belt or rope driven drive? State pro`s and con`s?
The advantages of using a chain drives are: > In a chain drive no slip occurrence takes place. > The chains take less space as compared to rope or belts as they are made of metal and offer much strength. > The chain drives can be used at both short and long ranges and they offer a high level of transmission efficiency. > Chain drives can transmit more load and power as compared to belts. > A very high speed ratio can be maintained in one step of chain drives.  Some of the cons of using a chain drive are: > The cost of producing chain drives is higher as compared to that of belts. > The chain drives must be serviced and maintained at regular intervals and henceforth their cost of ownership is high comparatively.
What are the different types of springs and explain them briefly?
Springs can be broadly classified into the following types: > Helical Springs: These springs as their name suggests are in coil form and are in the shape of helix. The primary purpose of such springs are to handle compressive and tensile loads. They can be further classified into two types: compression helical spring and tension helical spring each having their own unique areas of application./ > Conical and volute springs: Both these spring types have specialized areas of usage where springs with adaptable rate according to the load is required. In case of conical springs they are wound so as to have a uniform pitch while on the other hand volute springs are wound in a slight manner of a parabloid.  > Torsion Springs: The characteristics of such springs is that they tend to wind up by the load. They can be either helical or spiral in shape. These types of springs are used in circuit breaker mechanisms. > Leaf springs: These types of springs are comprised of metal plates of different lengths held together with the help of bolts and clamps. Commonly seen being used as suspensions for vehicles. > Disc Springs: As the name suggests such types of springs are comprised of conical discs held together by a bolt or tube. > Special Purpose Springs: These springs are all together made of different materials such as air and water.
During the design of a friction clutch what are the considerations that should be made?
In order to design a friction clutch the following points must be kept in mind: > The material for the contact surfaces must be carefully selected. > For high speed devices to minimize the inertia load of the clutch, low weight moving parts must be selected. > The contact of the friction surfaces must be maintained at all the times without the application of any external forces. > Provisions for the facilitation of repairs must be there. > In order to increase safety the projecting parts of a clutch must be covered. > A provision to take up the wearing of the contact surfaces must be present. > Heat dissipaters to take away the heat from the point of contacting surfaces must be there.
What are the different types of brakes and explain them briefly?
Brakes can be classified on the basis of their medium used to brake, they are as follows: > Hydraulic Brakes: These brakes as their name suggest use a fluid medium to push or repel the brake pads for braking. > Electric Brakes: These brakes use electrical energy to deplete or create a braking force. Both the above types of breaks are used primarily for applications where a large amount of energy is to be transformed. > Mechanical Brakes: They can be further classified on the basis of the direction of their acting force: Radial Brakes: As their names suggests the force that acts on the brakes is of radial direction. They can further be classified into internal and external blades. Axial Brakes: In these types of brakes the braking force is acting in an axial direction as compared to radial brakes.
On what basis can sliding contact bearings be classified? Explain?
Sliding contact bearings can be classified on the basis of the thickness of the lubricating agent layer between the bearing and the journal. They can be classified as follows: > Thick film bearings: These type of bearings have their working surface separated by a layer of the lubricant. They are also known as hydrodynamic lubricated bearings. > Thin film bearings: In this type of bearings the surfaces are partially in direct contact with each other even after the presence of a lubricant. The other name for such type of bearings is boundary lubricated bearings. > Zero Film Bearings: These type of bearings as their name suggests have no lubricant present between the contact layers. > Externally or hydrostatically pressurized lubricated bearings: These bearings are able to without any relative motion support steady loads.
What are the basis on which the best material for Sliding Contact Bearings manufacturing?
Some of the important properties to lookout for in the material for sliding contact bearings are as follows: > Compressive Strength: In order to prevent the permanent deformation and intrusion of the bearing the material selected should be possess a high compressive strength to bear the max bearing pressure. > Fatigue Strength: the material selected for the bearing should be able to withstand loads without any surface fatigue cracks getting created. This is only possible if the material has a high level of fatigue strength. > Comfortability: The material should be able to adjust or accommodate bearing inaccuracies and deflections without much wear and heating. > Embeddability: The material should allow the embedding of small particles without effecting the material of the journal. > Bondability: The bearings may be created by bringing together ( bonding ) multiple layers of the material. Due to the above reason the bondability of the material should be sufficiently high. > Thermal conductivity and corrosion resistance: Thermal conductivity is an essential property for bearing materials as it can help in quickly dissipating the generated heat. Also the material should have a level of corrosion resistance against the lubricanBriefly explain the advantages of Cycloidal and Involute gears?
The advantages of the Cycloidal gears are as follows:  > Having a wider flank as compared to Involute gears they are considered to have more strength and hence can withstand further load and stress. > The contact in case of cycloidal gears is between the concave surface and the convex flank. This results in less wear and tear. > No interference occurs in these types of gears.  The advantages of Involute gears are as follows: > The primary advantage of involute gears is that it allows the changing of the centre distance of a pair without changing the velocity ratio.  > The pressure angle remains constant from start to end teeth, this results in less wear and smooth running of the gears. > The involute gears are easier to manufacture as they can be generated in a single curve ( the face and flank ).
How can the reaction of support of a frame be evaluated?
Generally roller or hinged support are used to support the frames. The conditions of equilibrium are used to determine the reaction support of a frame. The condition of equilibrium takes place when the sum of the horizontal and vertical forces sum equal to zero. The system must form a state of equilibrium even after considering the external loads and the reactions at the supports. For equilibrium to be prevalent in the system the following conditions are required to be in occurrence: > Summation of V = 0. This implies that the summation of all the forces in the vertical direction results to zero. > Summation of H = 0 . This implies that the total of all the forces acting in horizontal direction is also zero. > Summation of M = 0. The sum of all the moment of forces around a point must be zero.
Explain in an orderly manner how the force in the member of a truss be detected using the method of joint.
The steps required to calculate the force are as follows: > The reaction at the support has to be first calculated. > Once the reaction is calculated the direction of force of the member is made to make it tensile. On getting the result to be negative the direction assumed is wrong and this implies the force being compressive in nature. > A joint needs to be selected whose 2 members are not known. The lami`s theorem is used on the joint on which less than three forces are acting. > After the above process is complete the free body diagrams of the joint needs to be made. Since the system is in equilibrium the condition of Summation of V and H must result in zero.  > After the above step the resolution of forces method needs to be used on the joint on which more than 4 forces are acting.
In order to derive the torsional formulas what are the assumptions taken?
The torsion equation is derived on the basis of following assumptions: > The shaft material is uniform, throughout the shaft. > Even after loading the shaft circular remains circular. > After the application of torques the plain section of a shaft remains plain. > Any twist that occurs in the shaft remains uniform and constant. > After the application of torque the distance between any two cross-sectional references remains constant. > The elastic limit value of a shaft is never exceeded even after the shear stress induced because of torque application.
What are Bevel Gears and what are its types?
Bevel gears are the type of gears in which the two shafts happen to intersect. The gear faces which are tooth bearing are conical in shape. They are generally mounted on shafts which are 90 degrees apart but they can be made to work at other angles as well. The bevel gears are classified into the following types on the basis of pitch surfaces and shaft angles: > Mitre Gears: These types of gears are similar to each other ie. they have the same pitch angles and contain the same number of teeth. The shaft axes intersect at 90 degrees angle. > Angular bevel gears: When two bevel gears connect at any angle apart from 90 degrees. > Crown bevel gears: When the two shaft axes intersect at an angle greater than 90 and one of the bevel gears have a pitch angle of 90 degrees they are known as crown bevel gears. > Internal bevel gears: In these type of gears the teeth on the gears is cut on the inside area of the pitch cone.
What are the different values that need to be determined in order to design a cylinder for an ICE?
The following values are needed to be determined: > Thickness of the cylinder wall: The cylinder walls in an engine is made witness to gas pressure and the side thrust of a piston. This results in two types of stresses: longitudinal and circumferential stress. Both the types of stresses are perpendicular to each other and hence it is aimed to reduce the resulting stress as much as possible. > Length and bore of the cylinder: The length of the cylinder and the length of the stroke is calculated on the basis of the formula: length of cylinder L = 1.15 times the length of the stroke (l). L = 1.15(l) > Cylinder flange and studs: The cylinders are always cast integral as a part of the upper crankcase or in some cases attached to it by means of nuts and bolts. The flange is integral to a cylinder and henceforth its thickness should be greater than that of the cylinder wall. The thickness of flange should generally be between 1.2t-1.4t where t is the cylinder thickness. The stud diameter is calculated by equating gas load ( due to max pressure ) to the grand total of all the resisting forces of the studs.
What are considerations taken into account while creating a piston head?
The piston head is designed on the basis of the following considerations: > The crown should have enough strength to absorb the explosion pressure inside the engine cylinder. > The head must always dissipate the heat of the explosion as quickly as possible to the engine walls. The thickness of the head is calculated on the basis of another formula which takes into consideration the heat flowing through the head, the conductivity factor of the material. The temperature at the center and edges of the head. > The thickness of the piston head is calculated on the basis of the Grashoff`s formula which takes into consideration the maximum gas pressure of an explosion , the permissible bending and the outside diameter of the piston.
Civil Engineering interview questions and answers
1. How can you distinguish between sorption, absorption and adsorption?
2. What is modular elasticity?
3. Discuss some applications of modular elasticity.
4. What is difference between engineering stress and true stress?
5. What are some structures that are subjected to fatigue?
6. What is the tensile strength of wood?
7. Explain soil analysis?
8. What is soil enforcement?
9. How can you achieve soil enforcement?
10. What is a bearing capacity of soil?
11. Why does the pressure increase under soil?
12. How to increase a bearing capacity of soil?
13. What you understand by building codes?
14. Explain moment of inertia and its importance.
15. Which is the best book for building construction?
16. How do we determine the specific gravity of a cement?
17. What are the causes of building collapse?
18. Explain the latest method to detect a crack in a building?
19. How do we test on design and style in a software?
20. Explain different types of RCC pipes.
21. Explain the design for RCC multi-storied building?
22. What are the benefits of RCC pipes over steel designed pipes?
23. Elaborate advantages & disadvantages of using crusher dust instead of sand in RCC work.
24. How can you produce desired alloys and discuss their applications in daily life.
25. Can inverted beams used in pipes during construction? If yes, explain how it can be implemented?
26. What is rigging?
27. What are the techniques to measure road difference?
28. Explain major differences between routing maintenance and major maintenance.
29. What you understand by Richter scale?
30. How do we calculate the power of centrifugal pump?
31. What is a tensile strength? What is the tensile strength of wood? 32. Difference between pre-tensioning and post-tensioning.
33. Explain the difference between shear and tensile strength.
34. Why the statue of liberty is made of Copper?
35. What is the difference between TOR steel and TMT steel?
36. Which code is used for TOR & TMT steel bar?
37. Explain major difference between auto level and dumpy level?
38. What is the L/D ratio of cantilever beam?
39. What is the ratio of steel and concrete to use in slabs , beams, columns ?
40. What is pre-stressed concrete?
41. What are the ingredients of pre-stressed concrete?
42. What do you mean by honeycomb in concrete?
43. Why is concrete cube test carried out?
44. How do you calculate the power of centrifugal pump?
45. What is aggregate?
46. What is absolute pressure? How absolute pressure is calculated? 47. What is the absolute pressure scale?
48. What is gravity flow? 49. What is a projection line?
50. What is horizon or horizontal mining?
What are the steps involved in the concreting process, explain?
The major steps involved in the process of concreting are as follows: 1. Batching 2. Mixing 3. Transporting and placing of concrete 4. Compacting. > Batching: The process of measurement of the different materials for the making of concrete is known as batching. batching is usually done in two ways: volume batching and weight batching. In case of volume batching the measurement is done in the form of volume whereas in the case of weight batching it is done by the weight. > Mixing: In order to create good concrete the mixing of the materials should be first done in dry condition and after it wet condition. The two general methods of mixing are: hand mixing and machine mixing. > Transportation and placing of concrete: Once the concrete mixture is created it must be transported to its final location. The concrete is placed on form works and should always be dropped on its final location as closely as possible. > Compaction of concrete: When concrete is placed it can have air bubbles entrapped in it which can lead to the reduction of the strength by 30%. In order to reduce the air bubbles the process of compaction is performed. Compaction is generally performed in two ways: by hand or by the use of vibrators.
Describe briefly the various methods of concrete curing.
Curing is the process of maintaining the moisture and temperature conditions for freshly deployed concrete. This is done for small duration of time to allow the hardening of concrete. The methods that are involved in saving the shrinkage of the concrete includes: (a) Spraying of water: on walls, and columns can be cured by sprinkling water.  (b) Wet covering of surface: can be cured by using the surface with wet gunny bags or straw (c) Ponding: the horizontal surfaces including the slab and floors can be cured by stagnating the water. (d) Steam curing: of pre-fabricated concrete units steam can be cured by passing it over the units that are under closed chambers. It allows faster curing process and results in faster recovery.  (e) Application of curing compounds: compounds having calcium chloride can be applied on curing surface. This keeps the surface wet for a very long time.
What do you understand by “preset” during the installation process of bridge bearings?
During the installation of bridge bearings the size of the upper plates is reduced to save the material costs. This process is known as preset. Generally the upper bearing plate comprises of the following components: > Length of bearing > 2 x irreversible movement. > 2 x reversible movement. The bearing initially is placed right in the middle point of the upper bearing plate. No directional effects of irreversible movement is considered. But since the irreversible movement usually takes place in one direction only the displaced direction is placed away from the midpoint. In such cases the length of the upper plate is equal to the length of the length of the bearing + irreversible movement + 2 x reversible movement.
Why are steel plates inserted inside bearings in elastomeric bearings?
In order to make a elastomeric bearing act/ function as a soft spring it should be made to allow it to bulge laterally and also the stiffness compression can be increased by simply increasing the limiting amount of the lateral bulging. In many cases in order to increase the compression stiffness of the bearing the usage of metal plates is made. Once steel plates are included in the bearings the freedom of the bulge is restricted dramatically, also the deflection of the bearing is reduced as compared to a bearing without the presence of steel plates. The tensile stresses of the bearings are induced into the steel plates. But the presence of the metal plates does not affect the shear stiffness of the bearings.
What reinforcements are used in the process of prestressing?
The major types of reinforcements used in prestressing are: > Spalling Reinforcement: The spalling stresses leads to stress behind the loaded area of the anchor blocks. This results in the breaking off of the surface concrete. The most likely causes of such types of stresses are Poisson`s effects strain interoperability or by the stress trajectory shapes. > Equilibrium reinforcements: This type of reinforcements are required where several anchorages exist where the prestressing loads are applied in a sequential manner. > Bursting Reinforcements: These kinds of stresses occur in cases where the stress trajectories are concave towards the line of action of load. In order to reduce such stresses reinforcements in the form of bursting is required.
In the design of bridge arguments what considerations should be made to select the orientation of the wing walls?
Some of the most common arrangements of wing walls in cases of bridge arguments are as follows: > Wing walls parallel to abutments: This method is considered to take least amount of time to build and is simple as well. But on the downside this method is not the most economical. The advantage of this type of design being that they cause the least amount of disturbance to the slope embankment. > Wing walls at an angle to abutments: This design method is considered to be the most economical in terms of material cost. > Wing walls perpendicular to abutments: The characteristic of this design is it provides an alignment continuous with the bridge decks lending a support to the parapets.
In case if concrete box girder bridges how is the number of cells determined?
When the depth of a box girder bridge exceed 1/6th or 1/5th of the bridge width then the design recommended is that of a single cell box girder bridge. But in case the depth of the bridge is lower than 1/6th of the bridge width then a twin-cell or in some cases multiple cell is the preferred choice. One should also note that even in the cases of wider bridges where there depths are comparatively low the number of cells should be minimized. This is so as there is noticeably not much improvement in the transverse load distribution when the number of cells of the box girder is higher than three or more.
Under what circumstances should pot bearings be used instead of elastomeric bearings?
Pot bearings are preferred over elastomeric bearings in situations where there are chances of high vertical loads in combinations of very large angle of rotations. Elastomeric bearings always require a large bearing surface so that a compression is maintained between the contact surfaces in between the piers and the bearings. This is not possible to maintained in high load and rotation environment. Also the usage of elastomeric bearings leads to the uneven distribution of stress on the piers. This results in some highly induced stresses to be targeted at the piers henceforth damaging them. Due to the above reasons pot bearings are preferred over elastomeric bearings in such cases.Why should pumping be not used in case of concreting works?
During the pumping operation the pump exerted pressure must overcome any friction between the pumping pipes and the concrete, also the weight of the concrete and the pressure head when the concrete is placed above the pumps. Since only water is pump able, all the pressure generated is by the water that is present in the concrete. The major problem due to pumping are segregation effects and bleeding. In order to rectify and reduce these effects, generally the proportion of the cement is increased in order to increase the cohesion , which leads to the reduction of segregation and bleeding. Also if a proper selection of the aggregate grading can vastly improve the concrete pump ability.
Why should curing not be done by ponding and polythene sheets?
The primary purpose of curing is to reduce the heat loss of concrete that is freshly placed to the atmosphere and in order to reduce the temperature gradient across the cross-section of the concrete. Ponding is not preferred for curing as this method of thermal curing is greatly affected by cold winds. In addition to that in ponding large amounts of water is used and has to be disposed off from the construction sites. Polythene sheets are used on the basis that it creates an airtight environment around the concrete surface henceforth reducing the chances of evaporation over fresh concrete surfaces. But the usage of polythene can be a drawback as it can be easily blown away by winds and also the water lost by self-desiccation cannot be replenished.
What are the different type of slump test indications?
Slump tests are performed to empirically measure the workability of fresh concrete. It is used to measure the consistency of the concrete. In general there are three different types of slumps that occur in slump tests. They are as follows: > True Slump > Shear Slump > Collapse Slump True Slump: This type of slump is characterized by the general drop of the concrete mass evenly without visible signs of deterioration or disintegration.  Shear Slump: It indicates that the concrete mix is deficient in cohesion. This type of slump leads to segregation and bleeding. Henceforth in the long run effecting the durability of the concrete.  Collapse Slump: This type of slump is indicates that the mix of concrete is simply too wet. The mix is considered to be harsh and lean
Why is propping required for long structures once the formwork is removed?
Once the process of concreting is performed the striking of the formworks should be done as soon as possible as delay in this process can lead to the discoloration of the concrete structures. In case of long structures particularly long span structures once the structures have attained enough strength to support themselves it is essential to provide them with propping as creep deflection can take place which can greatly reduce the integrity of the structure. Due to the above mentioned reasons propping should be done after the removal of formwork. Also the props should not be made to stand long as it can lead to overstress for the structures.
Explain the mechanism of cavitations in pipes and drains?
The formation of air bubbles in a fluid due to low pressure conditions lower than the saturation pressure is known as cavitations. This is considered to be a high potential damage condition where the strength and durability of the pipes can be greatly reduced. Cavitation works on the principle of Bernoulli’s Equation. When fluids are at high velocities the pressure head of fluids reduce accordingly. But since the fluid pressure is lower than the saturation pressure the dissolved gases get released from the flowing fluid. These air bubbles suddenly collapse on entering a region of high pressure. This leads to the damage of the pipelines as a high level of dynamic pressure is created.
For what purpose bedding is used under storm water drains, explain?
Beddings are primarily made up of granular or concrete materials. They are primarily used for the following purposes: > They are used to provide a more uniform support for the under pipes so that the bending moment longitudinally can be reduced greatly.  > In order to enable the pipes to get more load-supporting strength. > They are also used to act as a platform to achieve a more correct alignment and level pre and post construction. > In case of pipes which contain spigot and socket joints, it enables pipes to get supported along pipe lengths in place of sockets. Otherwise it can lead to uneven stress being induced on the pipes eventually damaging it.Why are pull-out tests performed for soil nails?
Pull out tests are performed for primarily the following reasons: > In order to detect and the verification of the bond strength among the soil and the grout adopted during the design of soil nails. This is considered to be as the primary objective of performing pull out tests for soil nails. > For the detection of any slippage or occurrence of creeps. > To detect the elastic and deformations (plastic) of any of the test nails employed. Observations are made during the loading and unloading cycles of the soil nails repetitively. > To achieve the perfect balance the test nails should always be loaded so that the ultimate soil/grout mixture with an upper limit of 80%.
Describe briefly the advantages and disadvantages of using plastic and timber fenders?
The advantages and disadvantages of using plastic fenders are as follows: Plastic fenders are low in strength with a relatively high resistance to abrasion. Plastic fenders are resistant to chemical and biological attacks. Plastic fenders have moderate energy absorption capacity. The berthing reactions are also comparatively moderate and depends on the point of contact. Also since they are made from recycled material they are environmental friendly. The advantages and disadvantages of using timber fenders are: timber fenders are low in strength and are very susceptible to marine borer attacks and rotting. The energy absorption capacity is very low. Also generally the contact pressure between the vessels and the fender are high.
Explain why concrete barriers have curved surface profiles?
The concrete safety fencings are made to contain vehicles in their carriageway being travelled so as to reduce the chances of rebounding into the roads leading to more hazards. In the case of normal fencings upon vehicle crashes the fencings give away so as to absorb as much energy as possible henceforth reducing the impact on the vehicles. But in the case of concrete barriers their purpose is not to absorb energy of vehicles crashing into the barrier but to retain them. They have a curved design so as to allow the vehicles that hit them to slightly go up on the barrier but not overturn. They also prevent the vehicle from again getting back on the road by rebounds. This helps in vastly reducing the chances of other vehicle hazards.
Why is the use of granular sub-base in concrete carriageways not preferred, explain?
Some of the reasons why granular sub-base is not preferred in concrete carriageways: > Sub bases are permeable and hence water can seep through them easily. The soil particles get pumped out through the joints on the application of traffic loads. This results in the creation of voids underneath the pavement structure. This leads to the weakening of the concrete surface and it can crack easily upon intense traffic loads. > Instead if lean concrete is used for carriageways it greatly increases the strength of the roads and the load carrying capacity of the roads is increased. > Sub-bases implementation requires a lot of workmanship which can lead to an un-uniform distribution of the sub-base. This can lead to the cracking of the carriageway when there is severe traffic loading.
Why are separation membranes used between concrete pavement slab and sub-base?
The purpose of separation membrane between the concrete pavement slab and the sub-base are as follows: > The separation membrane reduces the frictional forces between the concrete slabs and the sub-base. The membrane aids the movement of the concrete slab in reference to the sub-base when changes in the level of the moisture and temperature occurs. > It aids in the segregation of sub-base materials from freshly placed concrete. > The separation membrane also helps in the reduction of cement and water loss in the form of immature concrete. Immature concrete greatly affects the strength of the concrete. It also affects the durability of it.  A good example of a separation membranes is polythene sheeting which is commonly used.
In the roof of a pumping station explain briefly the components of a waterproofing system.
The components of a typical waterproofing system on the roof of a pumping station are as follows: > Right above the structural finish level of the roof ( concrete ) a uniform thickness screed is applied so as to facilitate the application of the waterproofing membrane. The surface provide for the membrane should always possess good cohesion properties and must be thin so as to prevent any un-uniformity. This thin layer also acts as a layer of thermal insulation. > Right above this layer the waterproofing membrane is deployed to secure the water tightness of the roof. > In order to enhance the thermal insulation of the roof an insulation board is sometime placed right above the waterproof membrane. The insulation board helps in the maintenance of a stable temperature in both weathers.
 During reclamation how can the occurrence of mud waves can be rectified?
There are several solution to the rectification of the problem of mud waves: > Complete removal of all the disturbed mud: This method can be considered to be one of the fastest methods. As soon as the disturbed mud is removed some filling material is used to replace the disturbed mud. But economically this method can be expensive as compared to others. > Accelerated consolidation of disturbed mud: In this method surcharging loads are placed on top of the mud waves. Along with this band drains are installed to accelerate the consolidation process. This method is quite slow compared to the other methods. > Partial removal of the disturbed mud: This method is the hybrid of the above two methods where the top layer is removed whereas the lower level is treated with the surcharging process.
 In reclamation works what are the importance of geotextiles and sand?
The primary purposes of geotextiles and sand in reclamation works are as follows: > Geotextiles: They are used to separate the marine mud from the reclamation fill. Also geotextiles are used as reinforcements in reclamation processes to increase its stability. It is still debated as to whether the usage of geotextiles is better or are the old processes followed are better as the performance has not been comparable to the conventional methods. > Sand: In reclamation process sand is used to spread the load of any future public dumps placed on top of it. Sand also acts as a drainage for the excess pore water pressure of band drain installations.
In block work seawalls what is the purpose of slip joints?
Joints which are formed from the cope level to the toe level of seawalls through a complete vertical plane are known as slip joints. Such joints are designed so as to handle the differential settlements between the seawalls adjacent panels. In the slip joints the aggregates inside the half-rounds channels enables some vertical movements. These vertical movements are induced by differential settlements. This enables in the interlocking of the adjacent panels of the seawalls to link the panels in one unit against the earth pressure ( lateral ) which is exerted on the seawalls.
For a washout valve why are two gate valves required in normal practice?
The washout valves are primarily used for normal maintenance works such as that of water main. This can be like to allow water to flow out during the cleaning of the water main. The junctions at which a pipe branches out to a washout point usually a gate valve is installed so that the two pipelines are separated. The gate valve installed above usually remains open during normal operation. Another gate valve is installed further downstream and this remains closed during normal operation of the washout valve. In case this valve is not installed then the pipe section of the branched out pipe would remain dry during normal operation and high chances of damage and leakage can take place. When the downstream valve is installed the branched out water main contains water under normal operation. With two gate valves installed a leakage can be detected immediately.
What are the different approaches in designing the floors of the service reservoirs?
In general there are two main approaches of designing the reservoir floors to prevent leakage of water due to seasonal and shrinkage movements: > In this approach the movement joints of the reservoir floor panels are such that the free expansion and contraction of the panels takes place. Every panel is isolated from the other panels and two panels have a sliding layer between them to help in sliding. > The second method does not provide any room for free movement. With seasonal and shrinkage movements, some cracks are designed to voluntarily occur on the floors of the service reservoirs. These tiny cracks are spread throughout the floor and are simply too minute to cause any leakage or corrosion of the floors. But the difference also in this method is that the amount of reinforcement used is much more than the first approach.
Electronics Communications interview questions and answers
1. What is DMA controller?
2. What is DMA channels?
3. What happens during DMA transfer?
4. What is half duplex transmission?
5. What is the difference between the bandwidth of half duplex and simplex transmission?
6. What are the processes required to perform interfacing successfully?
7. What is single input output interface? How it is different from single ended interface?
8. How does data transfer takes place between memory and input output ports?
9. What is parallel data transfer process?
10. Differentiate between PPI and input output devices.
11. What is parallel to serial conversion?
12. Explain the working of stepping motors.
13. What are the data pins of microprocessors? What is their use?
14. What is working principle of Profibus and how it transfer data?
15. Explain zener breakdown and avalanche breakdown?
16. What is the need of filtering ideal response of filters and actual response of filters? What is sampling theorem? What is impulse response?
17. What are advantages of dc supply over ac supply?
18. What is the voltage level of noise signal?
19. What happens when a magnetic material is heated strongly?
20. What is the effect of polarization of dielectric under heat?
21. Which number system is used in analysing and programming of microprocessors?
22. What happens when an inverter is placed between both inputs of S-K flip flop?
23. What is the chief characteristics of master-slave flip flop? .
24. What logic function is obtained by adding an inverter to the output of an AND gate?
25. Which register which contains the instruction that is to be executed?
26. Which is used as storage location in the ALU and the control section of a computer?
27. What is simulator programme?
28. In C programming language, how many parameters can be passed to a function ?
29. Which filter has the highest Q factor?
30. What is multiplexing? Explain its primary advantage.
31. What is SSB modulation?
32. How can we remove unwanted sideband from SSB modulation?
33. How many channels are there in 2MB pulse code modulation?
34. What is cut off frequency?
35. Differentiate between pass band and stop band.
36. Explain Shanon-hartley law.
37. Why interlacing is used in television?
38. Which type of modulation is used in TV transmission?
39. What is attenuation?
40. Differentiate between transducer and transponder.
41. What is op-amp?
42. Differentiate between conductor and inductor.
43. What is meant by pre-emphasis and de-emphasis?
44. Which semiconductor device is used as a voltage regulator and why?
45. What are monitoring methods for Electronics activities?
46. What is an interrupt?
What are different categories of antenna and give an example of each?
Different categories of antenna are as follows : 1. Wire Antennas – Short Dipole Antenna 2. Microstrip Antennas – Rectangular Microstrip (Patch) Antennas 3. Reflector Antennas – Corner Reflector 4. Travelling Wave Antennas – Helical Antennas 5. Aperture Antennas – Slot Antenna 6. Other Antennas – NFC Antennas
What is handover and what are its types?
Handover in mobile communication refers to the process of transferring a call from one network cell to another without breaking the call. There are two types of handover which are as follows : Hard Handoff : hard handoff is the process in which the cell connection is disconnected from the previous cell before it is made with the new one. Soft Handoff : It is the process in which a new connection is established first before disconnecting the old one. It is thus more efficient and smart.
What is ionospheric bending?
When a radio wave travels into the ionospheric layer it experiences refraction due to difference in density. The density of ionospheric layer is rarer than the layer below which causes the radio wave to be bent away from the normal. Also the radio wave experiences a force from the ions in the ionospheric layer. If incident at the correct angle the radio wave is completely reflected back to the inner atmosphere due to total internal reflection. This phenomenon is called ionospheric reflection and is used in mobile communication for radio wave propagation also known as ionospheric bending of radio waves.
What is CDMA?
CDMA stands for Code Division Multiple Access which uses digital format. In CDMA systems several transmissions via the radio interface take place simultaneously on the same frequency bandwidth. User data is combined at the transmitter’s side with a code, then transmitted. On air, all transmission get mixed. At the receiver’s side the same code is used as in the transmitter’s side. The code helps the receiver to filter the user information of the transmitter from incoming mixture of all transmissions on the same frequency band and same time.
Explain the concept of frequency re-use.
The whole of the geographical area is divided into hexagonal shape geometrical area called cell and each cell having its own transceiver. Each BTS (cell site) allocated different band of frequency or different channel. Each BTS antenna is designed in such a way that i cover cell area in which it is placed with frequency allotted without interfering other cell signals. The design process of selecting and allocating channel groups for all of the cellular base station within system is called frequency reuse.
Explain Bluetooth.
Bluetooth is designed to be a personal area network, where participating entities are mobile and require sporadic communication with others. It is omni directional i.e. it does not have line of sight limitation like infra red does. Ericsson started the work on Bluetooth and named it after the Danish king Harold Biuetooth. Bluetooth operates in the 2.4 GHz area of spectrum and provides a range of 10 metres. It offers transfer speeds of around 720 Kbps.
What are GPRS services?
GPRS services are defined to fall in one of the two categories :
– PTP ( Point to point) – PTM ( Point to Multipoint) Some of the GPRS services are not likely to be provided by network operators during early deployment of GPRS due in part to the phased development of standard. Market demand is another factor affecting the decision of operators regarding which services to offer first.
What are the advantages of CDMA?
Advantages of CDMa are as follows : 1. Frequency diversity : Transmission is spread out over a large bandwidth due to that less affected by noise. If bandwidth is increased S/N ratio increases, which means noise will be reduced. 2. Multiplication Resistance : Chipping codes used for CDMA not only exhibit low correlation but also low autocorrelation. Hence a version of the signal that is delayed by more than one chip interval does not interfere with dominant signal as in other multipath environments. 3. Privacy : Due to spread spectrum is obtained by the use of noise like signals, where each user has a unique code, so privacy is inherent. 4. Graceful Degradation. In CDMA, more users access the system simultaneously as compared to FDMa, TDMA.
What are the advantages of spread spectrum?
SPread spectrum has the following advantages : 1. No crosstalk interference. 2. Better voice quality/data integrity and less static noise. 3. Lowered susceptibility to multipath fading. 4. Inherent security. 5. Co-existence. 6. Longer operating distances. 7. Hard to detect. 8. Hard to intercept or demodulate. 9. Harder to jam than narrow bands. 10. Use of ranging and radar.
Explain the steps involved in demodulating a signal.
Once the signal is coded, modulated and then sent, the receiver must demodulate the signal. This is usually done in two steps : 1. Spectrum spreading (e.g., direct sequence or frequency hopping) modulation is removed. 2. The remaining information bearing signal is demodulated by multiplying with a local reference identical in structure and synchronised with received signal.
How can a Pseudo Random Noise COde be usable?
To be usable for direct sequence spreading, a PN code must meet the following conditions : 1. Sequence must be built from 2 levelled numbers. 2. The codes must have sharp autocorrelation peak to enable code synchronization. 3. Codes must have a low cross-correlation value, the lower it is, more are the number of users which can be allowed in the system. 4. The codes should be “balanced” i.e. the difference between ones and zeros in code may only be 1
 What are the drawbacks of walsh codes?
Walsh codes have the following drawbacks : 1. The codes do not have a single, narrow autocorrelation peak. 2. The spreading is not over the whole bandwidth; instead the energy is spread over a number of discrete frequency components. 3. Although the full sequence cross correlation is identically zero, this does not hold for a partial sequence cross correlation function. Thus advantage of using orthogonal codes is lost. 4. Orthogonality is also affected by channel properties like multi path.
Explain radio environment in building.
Building penetration : Building penetration depends on the material used for construction and architecture used. This varies building to building and is based on building construction. Building Height Effect : The signal strength is always higher at top floor and generally floor gain height is about 2.7dB/floor which is not dependent on building construction. Building Floor Reception : The signal isolation between floors in a multi floor building is on the average about 20dB. Within a floor of 150 * 150 feet, the propagation loss due to interior walls, depending on the wall materials is about 20 dB between the strong and the weak areas.
List some advantages of GSM.
Here are some advantages of GSM : 1. GSM is mature, this maturity means a more stable network with robust features. 2. Less signal deterioration inside buildings. 3. Ability to use repeaters. 4. Talk time is generally higher in GSM phones due to pulse nature of transmission. 5. The availability of Subscriber Identity Modules allows users to switch networks and handset at will. 6. GSM covers virtually all parts of world so international roaming is not a problem.
What are the various types of numbers for network identity?
Various types of number for network identity are as follows : 1. MSISDN ( Mobile station ISDN) Number : It is international mobile subscriber number which is normally called mobile number. It is unique worldwide. 2. MSRN ( Mobile Subscriber Routing Number) : MSRN is used during mobile terminate trunk call to provide location of mobile subscriber. 3. HON ( Hand Over Number ) : HON is used for providing information required to transfer call from one B?SC to another BSC or to another MSC. 4. ISMI ( International Mobile Subscriber Identity Number) : Purpose of ISMI is for location update and authentication. 5. TMSI ( Temporary Mobile Subscriber Identity ) : TMSI is used instead of IMSI to improve security efficiency of network. 6. IMEI : International Mobile Equipment Identity.
What are the functions of Base Station System ( BSS)?
Functions of BSS are as follows : 1. Radio path control. 2. BTS and TC control. 3. Connection establishment with MS-NSS. 4. Mobility management, speech transcoding. 5. Connection of statistical data.
What are the parts of Network Management System ( NMS )?
Following are the parts of network management system : 1. OMC : Operation and maintenance center – Computerized monitoring center. 2. NMC : Network Management Center – Centralized control of a network is done here. 3. OSS : Operation and support system – Used for supporting activities performed in an OMC and/or NMC.
What are applications of DSP?
Some selected applications or digital signal processing that are often encountered in daily life are listed as follows: 1. Telecommunication: Echo cancellation in telephone networks. 2. Military Radar signal processing 3. Consumer electronics Digital Audio/TV 4. Instrumentation and control 5. Image processing image representation, image compression 6. Speech processing speech analysis methods are used in automatic speech recognition 7. Medicine Medical diagnostic instrumentation such as computerised tomography (CT) 8. Seismology DSP techniques are employed in geophysical exploration for oil and gas. 9. Signal Filtering Removal of unwanted background noise.
What is analog-to-digital conversion of signals?
A discrete-time signal is defined by specifying its value only at discrete times, called sampling instants. When the sampled values are quantised and encoded, a digital signal is obtained. A digital signal is obtained from the analog signal by using an analog-to-digital converter. This entire process is referred to as the conversion of signals from analog to digital form.
What are the properties of ROC for z-Transform?
Properties of the ROC for the z-Transform : 1. X(z) converges uniformly if and only if the ROC of the z-transform X(z) of the sequence includes the unit circle. The ROC of X(z) consists of a ring in the z-plane centered about the origin. That is, the ROC of the z-transform of x(n) has values of z for which x(n) r-n is absolutely summable. 2. The ROC does not contain any poles. 3. When x(n) is of finite duration then the ROC is the entire z-plane, except possibly z=0 and/or z=infinity. 4. If x(n) is a right sided sequence, the ROC will not include infinity. 5. If x(n) is a left sided sequence, the ROC will not include z=0. However if x(n)=0 for all n>0, the ROC will include z=0. 6. If x(n) is two sided and if the circle |z| = r0 is in the ROC, then the ROC will consist of a ring in the z-plane that includes the circle |z|=r0. 7. If X(z) is rational, then the ROC extends to infinity, i.e. the ROC is bounded by poles. 8. If x(n) is causal, then the ROC includes z=infinity. 9. If x(n) is anti- causal, trhen the ROC includes z=0.
Telecommunications interview questions and answers
1. Differentiate between GSM and CDMA – Telecommunications
2.What is the need of CPG message in ISUP protocol? – Telecommunications
3.What is protocol testing? What types of tool used in telecom testing? – Telecommunications
4.What is MTU? – Telecommunications
5.What is bridging? – Telecommunications
6.What is SS7? – Telecommunications
7.What is broadband? – Telecommunications
8.What is Impulse Response? – Telecommunications
9.Explain about Infinite Impulse Response. – Telecommunications
10.Explain about Common-Mode Rejection Ration. – Telecommunications
11.Describe about Asynchronous Transmission. – Telecommunications
12.Describe Synchronous Transmission. – Telecommunications
13.Explain about Voice Over Internet Protocol. – Telecommunications
14.What equipment is needed for VOIP? – Telecommunications
15.What are the advantages of VOIP? – Telecommunications
16.Describe about TTCN-3. – Telecommunications
17.Describe about RX Lev Full. – Telecommunications
18.What is the functionality of TCSM? – Telecommunications
19.What is Simple Network Management Protocol? – Telecommunications
20.What are the reasons for call drop? – Telecommunications
  1. What is ISUP protocol? 2. Why CPG message is required in ISUP protocol? 3. If RF power is good then what is the best Rx and Tx power? 4. What do you mean by TSCM? 5. Which frequency is used in voice sampling? 6. What is SS-7 signaling system? 7. Where memory is allocated for variables in a program? 8. What are various statuses of kernel? 9. What is the maximum decimal place which can be accommodated in a byte? 10. How personal computer can act as terminal? 11. How connection is established in Datagram? 12. What is the time for 1 satellite hop in voice communication? 13. What is the maximum number of satellite hops allowed in voice communication? 14. How many channels a 2MB PCM (pulse code modulation) has? 15. What action is taken when the processor under execution is interrupted by a non-mask able interrupt? 16. How much voltage is required in subscriber loop connected to local exchange?  17. How many T1 facilities the company needs between its office and the PSTN if it has 47 digital telephones, each operating at 64kbps? 18. What is the type of signaling used between two exchanges?  19. Where conditional results after execution of an instruction in a micro processor are stored? 20. What is line of sight?  21. Why can I get the 512k service but not the 1Mb or 8Mb Broadband service? 22. What is Buffering? 23. What is a matrix? 24. What equipment do I need in order to be able to access Broadband? 25. What is a Broadband modem? 26. How can I connect several computers to the Internet with Global Telecom Broadband? 27. What is Broadband? 28. What is the procedure if I want to upgrade my Broadband account to a faster speed? 29. Who can I contact if I continue having problems with my Broadband service? 30. What are the terms and conditions of using Global Telecom Broadband? 31. Explain how the signal is amplified in fiber optic cable? 32. What is BTS? 33. What are its different configurations of BTS and what is the power consumption/peak current for each of these types of BTS? 34. Write very briefly the underlining functional concept of GSM and CDMA? 35. What is Bridging? 36. Difference between Router and Switch. 37. What are the different Types of polling in RLC A.M mode? 38. What information is passed between cell FACH and cell DCH states? 39. Why the main function of BTS is to air interface signaling? 40. What is TTCN-3? 41. What is the difference between Rx Lev Sub and Rx Lev Full? What you mean by Link Budget?  42. Explain different types of digital modulation techniques. 43. What is the maximum Tx configuration for GSM? How it can be managed? 44. What is the functionality of search window in CDMA? What is the difference between Ec/Io and Eb/No? 45. What is Blackberry?  46. Why Rx power in microwave not considered less then -30dn? 47. What is FCC and how does it relate to Bluetooth? 48. How does Bluetooth use frequency hopping for security? 49. What is a Bluetooth dongle? 50. Which Bluetooth version uses adaptive frequency hopping? 51. Which company originally conceived and developed Bluetooth? 52. What is the total number of masters and slaves in a piconet? 53. What is the frequency range used for Bluetooth in Europe and United States? 54. Why is walse code used? 55. Which technology is used in Bluetooth for avoiding interference? 56. What is the difference between Internet and ISDN?  57. What is the frequency range used for Bluetooth in Japan? 58. How many SCO links are there in a piconet? 59. What is FEC in Bluetooth? 60. What is the main difference between GSM & CDMA? Which is the digital modulation used today in telecommunication? (Whatever his question meant the answer was CDMA)? 61. How do you link a T1 from the 1st BTS to 2nd BTS 4? 62. Why can Bluetooth equipment integrate easily in TCP or IP network? 63. What is the difference between Internet and ISDN? Is both are same or is there any specific difference? 64. What is the different between CDU C and CDU A? 65. What is the difference between Diplexer and Duplexer and what position? 66. Explain LTE and GSM internetworking.
Differentiate between GSM and CDMA
GSM – GSM uses multiple frequencies. – Uses TDMA and FDMA for accessing signals. – The voice rate is 9.6 KBPS. – Uses less bandwidth. CDMA – CDMA uses single frequency as carrier. – The voice rate is 14.4 KBPS. – CDMA power control to access method is better as Phased Locked Loops are used. – Follows soft handoff, hence call handling is more efficient.
What is the need of CPG message in ISUP protocol?
– CPG message is sent by the switch towards originator. – When the switch receives the setup, the call is forwarded. – When the message is sent it is signaled that the call is progress. – During the setup or active phase of a call, a message is sent. – This signifies the relayed to the originating has occurred.
What is protocol testing? What types of tool used in telecom testing?
– Testing the functionality of the node to some standard message flow for compliance is known as protocol testing. – Tester is used to send the standard message to the node that is under test. – The testing tools used for protocol testing are: 1. Glomosim simulator – To test 100 nodes on single CPU. 2. Abacus5000 – To test SIP. 3. Etherpeek – To test IP. 4. Nethawk – for SS7 testing. 5. Wireshasrk – for SS7/IP testing. 6. K1297- for testing G20(tektronics).
What is MTU?
– Maximum Transmission Unit refers to the largest packet size. – MTU is for passing a communication protocol for a given layer. – Communication interfaces such as NIC, serial port are associated with MTU parameters. – MTU might be a fixed unit as per Ethernet recommended standards. – Higher band-width efficiency is achieved with a higher MTU.
What is bridging?
– One of the forward techniques to use in packet-switched networks. – Bridging makes no assumptions about the address location of the network. – Flooding and examination of the source addresses are the building blocks for received packet headers for locating unknown devices. – The address of the device and its location is recorded in MAC address table for further broadcasting, after locating the device. – Bridging refers to Transparent bridging that predominates in Ethernet. – Source route bridging is used for token ring networks.
What is SS7?
– A global standard for telecommunications for channel signaling.  – The Common Channel Signaling System (SS7 / C7) standard defines various procedures and protocols for Public Switch Switched Telephone Network to exchange information over digital signaling network. – Providing call control, remote network management is the primary functions of SS7. – Controlling messages are exchanged between SS7 telephone exchanges through SS7. – The messages are transformed from Signaling Points and SS7 Signaling Transfer Points.
What is broadband?
– Broadband is an internet access with high speed. – Unlike dial-up connection, broadband connection is permanently connected. – It allows internet and telephone calls to take place simultaneously. No new land line is required. – Modulation is done in broadband on signals to transform data better.
What is Impulse Response? – Telecommunications (06-28-2012)
What is Impulse Response?
– Impulse Response of a system is the result that is presented with a brief input signals. – Linear, Time-Invariant Systems are characterized by the response of their impulses. – It is easy to analyze the systems that implements transfer functions. This is done by Laplace transform of the impulse response function. – The output of the system can be determined in time domain by convolution of the input function with the impulse response function. – The response of impulse and the response of Kronecker delta input are finite, as it settles zero in a finite number of interval samples.  – This process is done by Finite Impulse Response filter.
Explain about Common-Mode Rejection Ration.
– CMRR is used for measuring the tendency of the device that is to reject the input signals. – These signals can be from both input leads. – CMRR at a high level is important, as the signals of interest are represented by a small set of fluctuations of voltage. – The voltage fluctuations are superimposed on, possibly a large voltage offset. – Superimposition of the signals might also be done, when the information of relevance is contained in the voltage difference between the two signals.
RE: Explain about Common-Mode Rejection Ration. – Telecommunications badal (07-29-2014)
correct your it is ”unwanted input signals ” not the ”input signal ” your first line of you answer.
RE: Explain about Common-Mode Rejection Ration. – Telecommunications priya (08-12-2015)
CMRR it is the ratio of the power of the differential gain to the common mode gain… and is used for measuring the tendency of the device that is to reject the i/p should be as high as possible.
Describe about Asynchronous Transmission.
– It uses the start and stop bits for signifying the beginning bit of ASCII character that is to be transmitted. – For instance, ‘0100 0001 would become ‘1 0100 0001 000 1 0’’. – The additional one bit at the beginning and ending of the transmission refers the receiver that a character is entering and the character is ended. – When data need to be sent intermittently, this method is used. – The start and stop bits are supposed to be opposite polarity. – By this process, the receiver recognizes the second packet of the information that is being sent.
Describe Synchronous Transmission.
– Synchronous transmission does not use start and stop bits, hence data transfer rate is quicker. – The transmission is synchronized by speeding up at both the sending and receiving ends. – This uses clock signals that are built at each component. – Continual stream of data is sent between two nodes. – Re-synchronization is one of the methods to address the lost bits. – This method uses check digits instead of parity bits for ensuring the byte is correctly being interpreted and received.
Explain about Voice Over Internet Protocol.
– VOIP is also known as broadband telephony. – VOIP is to route the voice conversations over the internet. – VOIP services convert telephonic signals into digital signals. – Voice traffic is transmitted over Internet Protocol based networks. – VOIP deploys a protocol known as session control protocol for controlling the set-up and tear-down of calls as well as audio codecs.
What equipment is needed for VOIP?
Following are the equipment that is needed for VOIP. – A Broadband connection. – VOIP enabled telephones. – Nexton Soft Switches – A Router – An Audiocodec – An Astric server – A dial-up connection can also be used for VOIP
What are the advantages of VOIP?
Following are the advantages of VOIP: – Call costs are cheaper than traditional telephone land line calls. – Upgrading is simple. – Can be integrated with existing telephone connection. – Calls are free with VOIP PC-to-PC, irrespective of distance. – Virtual number enables to make calls across the globe. – Any number of geographical areas can be purchased, that works very cheap. – Messaging is also possible with VOIP phone.
Describe about TTCN-3.
– Testing and Test Control Notation Version 3 is one of the strongly typed tests scripting language. – It is used testing of communicating systems conformance.  – TTCN-3 is utilized for specification of test infrastructure interfaces. – This process is implemented with concrete communication environments. – TTCN-3 has standardized adapter interfaces.
Describe about RX Lev Full.
– RX Lev Full is Mobile transmit measurement report . – This report is generated for every 480ms. – The multi frame contains 104 TDMA frames. – Among 104 frames 4 TDMA frames are used for decoding the BSIC. – Remaining frames are used for serving and neighboring cells. – The measurement of these remaining TDMA frames is RX Lev Full.
What is the functionality of TCSM?
– TCSM is an acronym for Transcoder/Sub-Multiplexer. – Interface traffic is carried through the radio frequency in the air. – Data is compressed for efficient transmission of data. – Original data of 64 KBPS on interface side is compressed to 13 KBPS on the air. – The compression is done by TCSM.
What is Simple Network Management Protocol?
– SNMP is one of the UDP-based network protocols. – Monitoring network-attached devices for various administrative attentions, is the main purpose of SNMP. – SNMP is one of the protocol suites that are designed by Internet Engineering Task Force. – It has application layer database schema, protocol, and a group of data objects. – The basic messages, SET, GET, GET-NEXT, GET-RESPONSE and TRAP are the common messages that communicates between the SNMP manager and the SNMP agent.
What are the reasons for call drop?
A call drop occurs when – Slips occur in media. – There is some antenna tilting. – Phone goes out of range. – Electric and mechanic tilts occur. – Signal interference occurs.
Chemical Engineering interview questions and answers
1. Do you have any idea on recombinant protein expression?
2. Do you have recombinant protein expression experience? Explain?
3. Explain the Deacon reaction?
4. Explain various protein purification techniques?
5. For a centrifugal pump if the pump is running and we close the discharge valve what is the effect?
6. How is plate heat exchangers used in an ammonia refrigeration system?
7. How can we derive power factor equation p=vi cos phi?
8. How can we measure entropy?
9. How FOULING effected the heat transfer rate?
10. How much experience you are having in commercial software for protein design?
11. How much maximum power can be generated by 320v, 10kg-cm synchronous motor if shaft is rotated mechanically at 50 to 60 rpm?
12. Is it possible to compare the resistance to chloride attack of several materials of construction?
13. Is petroleum a mixture of hydrocarbon?
14. What are some good estimates for heat transfer coefficients for coils in tanks?
15. What are the affinity laws associated with dynamics pumps?
16. What are the effects of oils on the properties of polyolefin’s?
17. What are the precautions u are taking while starting HT motors?
18. What are the steps involved in wine making?
19. What can cause bulk solids to stop flowing from a bin?
20. What does the catalytic converter on an automobile do?
21. What is a good estimate for the absolute roughness for epoxy lined carbon steel pipe?
22. What are the main terms in Unit Operations? What are its characteristics?
23. What is difference between overall heat transfer coefficient & individual heat transfer coefficient?
24. What is load and what are the types of load?
25. What are the apt definitions for apparent power, active power and reactive power? Explain about different types of lamps?
26. What is the difference between horizontal and vertical heat exchanger?
27. What is the discharge pressure formula, for calculating discharge pressure?
28. What is the Import Procurement Cycle? What are the customization steps in SAP?
29. What is the meaning of flaring?
30. What is the most common cause of solid size segregation in bulk solid systems?
31. What is the purpose of capacitor? What does capacitor load means? How does it connect?
32. What is the speed of a rotary drier?
33. What is the symbol of sodium?
34. What are the various utilities of the process plant?
35. What is unit operation?
36. What regulates, or gives a substance the viscosity it has?
37. What steps can be taken to avoid stress corrosion cracking (SCC) in steel vessels used for storing anhydrous ammonia?
38. Which is more effective, a single extraction with a large volume of solvent or several small volume extractions? Explain.
39. Which reformer efficiency wise best?
40. Which thing is responsible for making petroleum?
41. Why is post-weld heat treatment sometimes necessary for welded vessels?
42. What is happening when paint dries?
43. What is an additive?
44. What is a good source of information for the design of pressure vessels?
45. What are some of the consequences of an undersized kettle type re boiler?
46. Explain the functioning of a three-way catalytic converter.
47. How does a tank-blanketing valve operate?
48. What does the catalytic converter on an automobile really do?
49. What is a common failure mechanism for above ground atmospheric storage tanks?
50. What are some common precipitating agents used to remove metals from aqueous waste streams?
51. Are there any methods of preventing cracking of carbon steel welds in refining environments? 52. What type of flow measurement devices is best for slurries?
53. What chemical is used to expand air bags in such a short amount of time? What is the best way to configure a bypass line in slurry services?

For a given bulk solid how can the particle size distribution be determined?

In order to determine the particle size distribution the simplest method is to make use of a sieve stack. In this method a stack is created of with different mesh sizes at each stack level. The structure is such that the biggest mesh size is at the top and the smallest at the bottom. Once this setup is created the before beginning the weight and other values of the solid is noted down. Once this is done the solid is placed at the topmost cylinder and the entire setup is exposed to a combination of vertical and horizontal movements. This will make the solid pass through different mesh sizes in the process separating the different particles according to their sizes. There are other more advanced methods of determining the particle size distribution as well such as video imaging and laser diffraction as well.

What are the different characteristics that can affect the flow of bulk solids and how?

The main characteristics that can affect the flow of bulk solids are as follows: > Moisture Content: when the moisture content is high the bulk solids become sticky in nature. This moisture can sometimes be absorbed from the atmosphere by some solids. > Temperature: The flow of the bulk solids can be sometimes affected by the temperature and also the period for which it is exposed to a particular temperature. > Particle size: More cohesive particles are generally found in bulk solids that are finer. Round particles are handled easily in comparison to odd, unsymmetrical shapes. > Time at rest: Many times the flow of certain bulk solids is affected by the time for which it has been kept stagnant or at rest. The more it is kept at rest the more slow the bulk solid flows.

What do you understand by Wet bulb Globe temperature?

The wet bulb globe temperature index is used to measure the sultriness of the environment. The sultriness is calculated on the basis of the humidity affects, the air speed and temperature and also the sun`s radiant heating factor. The sultriness in some cases could be fatal and hence it is very important to keep this under consideration. The wet bulb globe temperature index number was developed in the 1950`s and is now accepted as an industry standard. It is comprised of three temperature readings: > Wet bulb temperature > Ordinary dry bulb temperature > Black bulb globe temperature

In case of welded vessels why is stress relieving in the form of post-weld treatment necessary?

When a metal is welded together the point at which the two surfaces are joined are subjected to very high temperatures. During this time period the metals can go through a lot of random metallurgical processes. This causes the metal to be harder and brittle. This depends on the amount of carbon content. In order to relieve the metal of these properties heat treatment is done on the affected areas. By doing so the affected areas ductility increases. In this process the heat is maintained in the affected metal according to the thickness of the metal. The temperature of the heat is calculated from the P number which is unique for a particular composition.

What significance the angle of repose holds in the chemical industry, Explain?

The angle of repose is a property of particulate solids. A conical pile is formed when a bulk solid is poured onto a flat surface. The angle formed between the flat surface and the pile edge is called the angle of repose. The angle of repose depends on the following factors: > Density of the material > Surface area > Coefficient of friction of the material A material having a low angle of repose would always create float piles as compared to materials with a high angle of repose. This is used in the designing of equipments which are used for particulate solids. In addition to that this angle can be used to calculate the size of the conveyor belt that is used to transfer the materials.

What are the design considerations for a piping system for the transfer of slurries?

The following points must be considered for designing a piping system to carry slurries: > The design of the piping system should be able to self drain. > At the sections of the pipe where self draining is not possible provision to install manual draining must be installed. > At certain points where the chances of plugging are high, rod-out or blow-out connections must be provided to clear the lines. > In order to make flushing possible clean-out connections should be installed on either side of the main valves. > For easy access all the manifolds should have flanged connections. > T-connections are a must for access flanges.

What are the problems that are associated with the expansion joints?

Expansion joints are said to be weak points that are used in piping. They are used to reduce the stress that comes in the piping while installing and implementing it. This allows minor piping to be settled during the joining function. Expansion joints can’t stand the stress that is being produced by the piping forces. The problems that have been given are as follows: >Expansion joints get dirty very easily and they tend to build up as the time progresses. >They include some weak points that can`t stand the stress of the piping. >The issues can be removed if the drains are installed properly and purging of the material is being done.

What is the method involved in analyzing powders for composition?

The method that is used to analyze powders for compositions called as Fourier transform-infrared spectroscopy. This method is widely used to send the light beams of varying wavelength passing through the sample that is given and the light that is reflected from there will be analyzed by spectroscopy. This method is used to find out the absorption of each wavelength. The wavelength is measured with the laser light that is being referenced and on the basis of that calculations will be performed. The method is adopted to measure the compositions with accuracy.

What are the methods involved to test helium leak testing in a vacuum system?

The helium gets detected when it is found in the location of suction line. The helium source is passed over the flanges and possible sources of leakage in the vacuum system. The monitoring of the system takes place to see the detector and the pump suction to be found for the detectable amount of helium. The pressure can be increased or decreased according to the environment. If the system is allowing the pressure and the vacuum at the same time then more pressure can be applied to set the leaks. An installation of IR unit can be done to suction the substance of the pump and the spraying will be done on the flanges.

hat are the criteria’s involved in choosing mass balances for components?

The mass balances are used to combine all the masses that are present in the substance and create an overall effect when it is combined with other factors. The equations can be set for the component to allow any of the components used in mass balances. The criterions on which the balances are dependent are as follows: > Need to find out which component(s) are involved in solving the equations, without proper information the equation can`t be solved. > Find out about the components about which the reasonable assumptions can be made. By doing this the process gets simplified and it will help in making quick calculations.

What are the assumptions made on conservation equation?

The conservation equation is applied to the property of the system. It can have complicated as well as easy to solve calculations: > Closed system: that doesn`t have flows out of the substance. It deals with the closed mass flow. The equation to calculate this is: Accumulation= Generation > Open system: that allows the substance to enter or leave the system. > Conserved state system: in which no generation of the quantities happens. The quantities in this doesn`t get created or destroyed. These quantities are useful to balance according to the users need. > Steady State system: in which no accumulation of the substance is in steady state. This system avoids having differential equations. The process needs to be validated before it can run in any state.

What is the procedure to estimate the friction factor involved in heat exchanger tubes?

The following procedure is involved in determining the factors used inside the heat exchanger tubes that are varying with the temperatures. These are as follows: >Determine the average of the temperature by taking the mean of all the temperatures stored in the processing line. >Check the condition of the fluid entering the line at around 300 Celsius and leaving at around 280 Celsius. >Determine the physical properties at the temperature of 290 Celsius and the friction factors of the tubes at the same temperature. >Use the formula to calculate the friction factor of the laminar flow in the case where the liquid is cooling: Mean temperature/((sum of viscosity/wall viscosity)*0.38) Where Bulk and wall is determined at mean temperature over the length of line. Use the formula to calculate the friction factor of the turbulent flow in the case where the liquid is cooling: > (Mean temperature + bulk properties / ((sum of viscosity/wall viscosity)*0.11))/(bulk viscosity/wall viscosity)*0.17

What is the use of gear pumps in motor?

Gear pumps uses meshing gears that allow the pump fluid to be displaced by the method of displacement. They are used for hydraulic fluid power applications. They are one of the key factors involved in chemical installation having a certain viscosity to pump fluid. This type of pumps uses positive displacement pump having high pressure and low capacities. This includes the ability to handle wide range of viscosities, and allow easy to build and maintain the pumps. The gear pumps are controlled through the motor speed. Gear pumps can’t handle high tolerances and the fluids that are free of abrasives.

What are the factors involved in considering the choice of dry screw compressor?

Screw compressors are made up of a pair of meshing helical screws that is used to compress the gases. The dry screw compressors are used to have a flow range of 85-170 m/h and the discharge pressure is of 2070-2760 kPa. The dry screw compressor consists of timing gears that is maintained aligned with the rotors. The effectiveness is dependent on the clearances that exist between the helical rotors and between the chambers used for sealing the compression cavities. They are compact and smooth having the limited vibration and require spring suspension as well.

What is the process of including heat exchangers in ammonia refrigeration system?

The heat exchangers are used in ammonia refrigeration system from a very long time. The heat exchanger used is having smaller sizes and they are equivalent to the tubular exchanger can. This process works best for flooded system that require a separate liquid from the vapor. The system that is explained consists of a vessel, a drum, and accumulator and header tank with the heat exchanger. It works like this: >Liquid ammonia moves from vessel to exchanger >Vapor is returned to middle of drum >Vapor is removed from the drum and liquid enters through exchanger as it has lower density than others entering at the same rate in the system

What is the method adopted to minimize shell side pressure drop in a shell?

The method of protecting the shell from the pressure drop is very essential as it is very critical stage, where if not taken care properly the shell has to be replaced due to its degradation. In this rods or tube protectors are used instead of plates in top rows. The use of these rods puts less pressure drop and provides better distribution of the pressure on the plate. The plate that is used causes an abrupt of 90 degree turn of shell stream and an extra pressure drop on the whole shell. Use of the tube protectors will allow the shell to be saved from this and maintains its longevity.

What are the strategies acquired to cure tube vibration and exchangers in a shell?

The strategies that can be followed are as follows: >To cure the tube vibration uses the tubes that doesn’t allow passing of the flow-induced vibrations through them and are longer in height than others. Usually the tubes supported >Are of 3-4 inch. To make the bundle stiff insert metal slats and rods between the tubes that is used in the process. >Add a shell nozzle opposite of the inlet to cut the flow of the velocity of the fluid in half. This solution works for non-removable bundles that can easily be solved also by adding a distributor belt on the shell. This might be expensive solution to adopt as it requires more man power and use of more tubes.

What are the factors involved in designing kettle type reboiler?

To design the kettle type reboiler the requirements that needed to be present are as follows: >The size of the kettle has to be determined. >Provide the space to slow down the vapor velocity of all the liquid droplets. >Deciding the destination where the vapor would be deposited. >Handling a distillation tower with the following property: large space, high efficiency and high reflux rate. >The height of the vapor space should be kept such that the differences in the temperature won’t affect the kettle. There should be high heat flux for the kettles that run on higher temperatures.

 What are the steps taken to operate a tank-blanketing valve?

The steps taken are as follows:  >Tank blanketing valves provide a way to prevent and control the fires in the flammable liquid storage tanks. >The vapors that are produced cannot be ignited if there is no supply of oxygen present at that time. >The oxygen in most of the cases being provided by the air that is drawn into tank from the atmosphere when the empty process is taking place. >Install tank blanketing valves with inlet connected to the inert gas that is kept under the pressure. And the tanks outlet is being placed in vapor space. >The pressure drop is happening in the tank at predetermined level where the blanketing valve allows the transfer of gas into vapor space.

What are the steps required to design a vapor-liquid separator or flash drum?

The steps that are required are as follows:  > The size of the vapor-liquid separator depends on the flow rate of vapor and the liquid that is coming out of the vessel. > Assumed from the flow rates that if they are known then the size can be found out. > Use vertical pressure vessel to set it up or install it at given location. > The length to diameter ratio will be taken to provide liquid inventory between the level of liquid and the bottom of the vessel. > Provide a blockage mesh section at the vapor outlet to let the vapor pass through the mesh that is taken and can successfully leave the vessel. > Let liquid flow control the level of the valve.

Why does catalytic converter used in an automobile?

The catalytic converter is a device that converts harmful compounds in harmless compounds. The compounds harmful in nature are as follows: > Hydrocarbons- this is in the form of unburned gasoline that creates pollution and is more harmful. > Carbon monoxide is very harmful gas formed by the combustion of gasoline and used mainly for fuels. > Nitrogen oxides is also one of the gases that is poisonous in nature and produced by the release of heat from the engines. The release of nitrogen from the engine gets mixed with the oxygen in the air. The catalyst converter takes these harmful gases and uses the catalyst that is coated on the ceramic honeycomb or beads and attached to the exhaust pipe. This converts the carbon monoxide in carbon dioxide and makes it easy for the nature to consume it. The hydrocarbon gets converted in carbon dioxide and water. Same way the nitrogen oxides also gets converted in nitrogen and oxygen.

What are the different ways in which solids can be blended?

There are various ways in which solids can be blended, some of the common methods are: > Convective mixing: In this type of mixing the group of particles of a solid is transferred from one place to another, vigorous repositioning takes place in this method. This type of mixing is prevalent in the Trough mixer. > Diffusion mixing: In this type of mixing a new interface is formed over which the particles of a solid are distributed. A good example of diffusion mixing is in the traditional barrel mixer, where a new interface is formed. > Shear Mixing: In this type of mixing slipping planes are created over which the group of particles of a solid are mixed.

What are the different types of equipments for the conveyance of solids?

The various types of equipments available for the conveyance of solids are as follows: > Gravity Chutes: This equipment relies on gravity for the solids to fall under. > Air Slides: In this equipment the particles are suspended in air, and flow at an angle to the horizontal. > Belt Conveyors: This equipments use a belt to transfer the solids. > Screw Conveyors: The solids are moved using a rotating helical impeller. > Bucket elevators: The solids are moved using buckets which are attached to a belt in motion. > Vibrating Conveyors: The solid particles are subjected to vibrations and travel over to a table in a series of steps. > Pneumatic/ Hydraulic Installations: The particles are transported over a stream of air or water.

 What are the reasons of removal of particles from effluent gas?

The main reasons for the removal of particles from effluent gas are: > In order to protect and maintain the health of the workers and operators in the plant. It is also done to protect the surrounding population. The primary danger is due to the inhaling of the dust particles which can cause health issues. > It is also done to minimize the chances of explosions. Many carbonaceous materials remain suspended in air and when mixed with finely powdered metals can form a highly combustible mixture.  > Particles are also removed to reduce the loss of valuable materials. > It can also be used to recycle the gas for ex in case of blast furnaces the gas is used to fire the stoves.

In a crusher where is the energy provided to it is used up for?

The energy fed to a crusher is utilized for the following purposes: > To produce the elastic deformation of the particles prior to the fracture of the particles. > In order to produce inelastic deformation this causes the particles to reduce in size. > The energy is also used to cause the equipments elastic distortion. > In the friction of the particles between themselves and between the machine. > The energy also gets used up in the form of heat, noise and vibration in the plant. > The energy also get used up in the friction losses in the plant. Most of the energy is lost and only some of it is properly utilized. Nowadays it is of prime importance to reduce the energy losses.

On what basis are materials to be crushed evaluated apart from size?

The choice of the crusher machine to be employed to crush the materials depends on the following properties apart from the size of it: > Hardness: The hardness affects the power consumption and the wearing of the machine. With hard materials it is necessary to use a low speed machine along with pressure lubrication. > Structure: Normal granular materials can be crushed by using compression and impact methods. On the other hand for fiber like materials compression and impact methods don’t work instead a tearing action is required. > Moisture content: The moisture content in the materials can greatly affect the choice of machines. In case of excess moisture the materials flow gets hindered and it is essential to prevent them from caking together and form balls. > Crushing Strength: The amount of power that is required to crush a material can be derived directly from the crushing strength of the material. > Friability: This property indicates the tendency of a material to fracture. > Stickiness: As the name suggests this property is used to evaluate how sticky a material is as a very high sticky material can clog the machinery.

What are the advantages of using a ball mill over other conventional methods of crushing?

The advantages of using a ball mill over other conventional methods are as follows: > The mill can be used in multiple modes. It can be used in both wet and dry modes. The wet mode helps in the removal of the product.  > The installation cost and the power consumption of the mill is low. > Since the mill can be used in an inert atmosphere hence it could be used for the crushing of explosive materials. > It can be used for any type of hardness materials and also the grinding medium is cheap. > It can also be used for continuous and batch operations. > The ball mill supports two types of grinding: > Open circuit grinding  > Closed circuit grinding

Mention some of the specialized grinding and crushing methods.

Some of the specially developed grinding and crushing methods are as follows: > Electrohydraulic crushing: In this method an underwater discharge is created from a high capacity capacitor. > Ultrasonic Grinding: This type of grinding the material id placed between a drive roll and plate both of which are ultrasonically activated. This process is used for grinding micro sized materials. > Cryogenic grinding: For certain materials effective grinding is not possible by conventional means such as rubber, textiles etc. In order to cope with this problem the material is frozen to ultra low temperatures using liquid nitrogen. Once the material is frozen it is grounded as per requirements. >Explosive Shattering: This type of shattering is still on experimental basis, it involves energy to be transmitted to the particles in the form of shockwaves from an explosion chamber.

What are the assumptions made for Kynch Theory?

The following assumptions are made for the Kynch Theory:  > Across the horizontal layer the particle concentration is uniform  > The effects of the wall can be ignored. > No differential settings of particles are considered due to shape, size or composition changes or differences. > The velocity at which particles fall depends only on the local concentration of the particles and nothing else. > The concentration is considered to be uniform throughout or it can be assumed to increase towards the bottom. > The velocity of sedimentation approaches zero as the concentration reaches the limiting value. This limiting value corresponds to the sediment layer at the bottom which gets deposited.

 What are the merits of using a falling film evaporator?

The advantages of using falling film evaporators are as follows: > These types of evaporators have very high heat transfer coefficients ranging from 2000-5000 W/m(square) for water and 500 to 1000 for organic liquids  > The residence times are short in case of heated surfaces, 5-10 seconds without recirculation > They have very low pressure drops, 0.2-0.5 kN/m(square) , > These evaporators are well suited for vacuum operations as well. > The evaporation ratios are very high. 70 per cent without and 95 per cent with recirculation, > They have a very wide operating range, they can provide as much as 400% of the minimum throughput, > In addition to the above advantages they have a low cost of operation and are less susceptible to fouling