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Multiple choice question for engineering

Set 1

1. Terminal table
a) Contains all constants in the program
b) Is a permanent table of decision rules in the form of patterns for matching with the uniform symbol table to discover syntactic structure
c) Consist of a full or partial list of the token is as they appear in the program created by lexical analysis and used for syntax analysis and interpretation
d) Is a permanent table which lists all keywords and special symbols of the language in symbolic form

View Answer

Answer: d [Reason:] A permanent database that has entry for each terminal symbols such as arithmetic operators, keywords, punctuation characters such as ‘;’, ‘,’etc. Fields: Name of the symbol.

2. Advantage of incorporating the macro-processor into pass 1 is that
a) Many functions have to be implemented twice
b) Functions are combined not necessarily creating intermediate files as output from the macro-processor and input to the assembler
c) More flexibility is provided to the programmer in that he may use all the features of the assembler in conjunction with macros
d) All of the mentioned

View Answer

Answer: d [Reason:] A general-purpose macro processor or general purpose pre-processor is a macro …designed primarily for string manipulation, macro definition.

3. Which of the following is a phase of a compilation process?
a) Lexical Analysis
b) Code Generation
c) Both of the mentioned
d) None of the mentioned

View Answer

Answer: c [Reason:] Lexical analysis and code generation is a phase of compilation process.

4. System program such a s compiler are designed so that they are
a) Re-enterable
b) Non reusable
c) Serially usable
d) None of the mentioned

View Answer

Answer: a [Reason:] Re-enterable is the keyword for compiler being designed.

5. A series of statements explaining how the data is to be processed is called
a) Assembly
b) Machine
c) COBOL
d) Program

View Answer

Answer: d [Reason:] A program is a sequence of instructions, written to perform a task by computer. It requires programs to function, typically executing the program’s instructions in a central processor.

6. A loader is a program that
a) Program that places functions into memory and prepares them for execution
b) Program that automates the translation of assembly language into machine language
c) Program accepting another program written in a high level language and produces as object program
d) None of the mentioned

View Answer

Answer: a [Reason:] A loader is the part of an operating system that is responsible for loading programs and libraries. It is important in the process of placing the programs into memory and executing them.

7. A system program that setup an executable program in main memory ready for execution is
a) Assembler
b) Linker
c) Loader
d) Load and go

View Answer

Answer: c [Reason:] A loader is the part of an operating system that is responsible for loading programs and libraries. It is one of the essential stages in the process of starting a program, as it places programs into memory and prepares them for execution.

8. Which of the following system program forgoes the production of object code to generate absolute machine code and load it into the physical main storage location from which it will be executed immediately upon completion of the assembly?
a) Two pass assembler
b) Load and go assembler
c) Macro processor
d) Linker

View Answer

Answer: b [Reason:] A load and go assembler generates absolute machine code and loads it to physical memory.

9. Uniform symbol table
a) Has all constants in the program
b) Permanent table of rules in the form of patterns for matching with the uniform symbol table to discover syntactic structure
c) Consists of full or partial list of the tokens as they appear in the program created by Lexical analysis and used for syntax analysis and interpretation
d) A permanent table which has all key words and special symbols of the language in symbolic form

View Answer

Answer: c [Reason:] Each pass scans the program, the first pass generates the symbol table and the second pass generates the machine code.

10. Assembler is a program that
a) Puts programs into memory and executes them
b) Translates the assembly language into machine language
c) Writes in high level language and produces an object program
d) None of the mentioned

View Answer

Answer: b [Reason:] An assembler is a program that takes basic computer instructions and converts them into a pattern of bits that the computer’s processor can use to perform its basic operations.

Set 2

1. For the given traction application using a dc series motor for a starting time ’t’ is applied. If this method is replaced by a series-parallel control, giving 50% time for each series and parallel. The saving in the starting energy of
a) 25%
b) zero
c) 50%
d) 75%

View Answer

Answer: a [Reason:] Initially let the energy utilized was 100% for time t.Then for 50% duration for series, energy used is 50%. For parallel operation for the same circuit, the resistance gets halved assuming the same machine. So, for 50% of the parallel operation, 25% of energy is only utilized. Hence total saving is 25%.

2. If two series motors are identically coupled. One is running as motor while other as generator. For this combination,the iron losses and frictional losses are found identical for
a) identical speed and excitation.
b) identical speed.
c) identical rating and construction
d) None of the mentioned.

View Answer

Answer: a [Reason:] For same iron and frictional losses, same frequency should be there. For that same speed must be run.

3. Hysteresis loss in a dc machine is _____ of rate of flow of air and _____ on frequency of _____
a) independent, dependent, magnetic reversal
b) independent, dependent, operation
c) dependent, independent, magnetic reversal
d) None of the mentioned

View Answer

Answer: a [Reason:] Hysteresis loss in a dc machine is independent of rate of flow of air and depends on frequency of magnetic reversal.

4. In dc machine iron losses cause
a) heating in core
b) loss in efficiency
c) rise in temperature of ventilating air
d) all of the mentioned

View Answer

Answer: a [Reason:] The iron losses cause heating of the core which causes reduction inefficiency and cooling air gets heated up.

5. For squirrel cage and slip ring induction motor, cooling methods is efficient in
a) squirrel cage induction motor
b) slip ring induction motor
c) both of the motors
d) none of the mentioned

View Answer

Answer: a [Reason:] As the squirrel cage induction motor has more ventilation and more space as compares to slip ring induction motor, there will be more efficient ways to cool down the squirrel cage motor.

6. If one of the phases of the supply breaks down, then the connected three phase induction motor
a) continues to run as a single phase induction motor, provided load does does not increase beyond 57.7%
b) stops operating after few seconds
c) continues to run as single phase induction motor
d) continues to run as two phase induction motor

View Answer

Answer: a [Reason:] When one of the phases breaks down then the other two phases will supply the rated current but the load should be reduced to 57.7%.

7. If one of the phases of RYB supply gets broken, then the temperature rise of the induction motor
a) remains same as before
b) reduces as compared to the normal operating temperature
c) reduces to temperature rise of corresponding single phase induction motor
d) increases

View Answer

Answer: a [Reason:] The current flowing in the armature will remain same so to maintain the flux requirements of the machine.Hence the temperature rise will also remain same as the current remains same.

8. A three phase induction motor is connected to the infinite bus operating at the normal conditions. There occurs an unbalancing in the supply, leading to
a) unequal heating losses
b) stopping of motor
c) increase in lower
d) None of the mentioned

View Answer

Answer: a [Reason:] The unbalancing in the supply phase will create an unbalanced distribution of the current in the phases, thereby unequal heating.

9. A peaky voltage supply is given to the 3 phase power transformer of the connection power system. These results into
a) reduction in iron losses
b) reduction in copper losses
c) increase in iron losses
d) reduction in noise

View Answer

Answer: a [Reason:] The flux wave will be sinusoidal in nature as the emf is peaky in nature. Sine wave has least losses when compared to other wave forms.

10. The iron losses in a saturated three phase alternator is lesser than the non-saturated three phase alternator.
a) True
b) False

View Answer

Answer: a [Reason:] The non-saturated reactance is greater than saturated reactance. So the reactive losses or iron losses will reduce due lesser contribution of the same.

11. The hydroelectric plants in the industry are best suited with
a) closed circuit air cooling
b) hydrogen gas
c) direct water
d) any of the mentioned.

View Answer

Answer: a [Reason:] The closed circuit is so used to reuse the air in the system , so that to save water again in the cooling system.

Set 3

1. Synchronous-induction coupled motors are required for
a) high starting torque applications
b) high pull out torque applications
c) high running torques applications
d) none of the mentioned

View Answer

Answer: a [Reason:] Induction motor provides high starting torque with proper values of slip ring terminal resistance. Coupled along with the synchronous motor it acts as an independent set and be employed in high torque application.

2. Which of the following can be used for braking purposes in electric trains?
a) Induction generator
b) Induction motor
c) Dc series motor
d) Dc differentially compounded generator

View Answer

Answer: a [Reason:] Induction generator runs at a speed greater than the synchronous speed. To apply in braking purposes the induction generator can be run in the opposite direction to that of the operating machine direction and stopped.

3. A synchronous motor absorbing 60 kW is connected in parallel with an continuous load of 240 kW operating at 0.8 power factor lag.What is the kVAR supplied by the synchronous motor to obtain a total power factor of 0.9 lagging?
a) 35, leading
b) 35, lagging
c) 145, leading
d) None of the mentioned

View Answer

Answer: a [Reason:] Total power = 240 + 60 = 300 kW cos(phi) = 0.90. Total reactive power = P*tan(phi) = 300*tan(25.8) = 180 kVAR Load kVAR = 240*tan(36.87) = 180 kVAR kVAR supplied by the motor = 145-180 = -35 or k3 kVAR leading.

4. The most widely used application of ac series motor is
a) electric traction upto 1600 kW
b) paper mills
c) welding
d) none of the mentioned

View Answer

Answer: d [Reason:] Ac series motor is dc series motor connected to ac supply having an unidirectional torque, which is not very high in magnitude.It is widely applicable for small torque requirements like portable drilling machines, mixers etc.

5. Universal motor is used in vacuum cleaners, table fans and portable drilling machine.
a) True
b) False

View Answer

Answer: a [Reason:] The universal motor is dc series motor with ac supply with smaller torque. So it can be used for lower torque applications.

6. _______ generator is used in arc welding purposes.
a) Differential compound dc
b) Dc series
c) Cumulative compounded dc
d) Shunt

View Answer

Answer: a [Reason:] The external characteristics of the differentially compound generator have minimum voltage for the high current voltages.This is best harnessed feature for a high current requirement by the welding application.

7. The dc series generator is employed as
a) a booster to maintain constant voltage at the end of the feeder.
b) for supplying traction load
c) for battery bank charging
d) none of the mentioned

View Answer

Answer: a [Reason:] Referring to the external characteristics of dc series generator shows that the terminal end voltage increases as the loading increases from no load to full load. In feeders due to variable requirements the voltage drops while transferring when loading is raised.

8. If it asked by the customer to provide tappings on the transformer, the most efficient and economical way to provide it at
a) middle of hv winding
b) phase end of hv winding
c) neutral end of hv winding
d) middle of lv winding

View Answer

Answer: a [Reason:] Tappings are provided to tap different levels of voltages at the high voltage end of the transformer.Providing it as low voltage side has no use and it is not economical.

9. In a single phase induction regulator, the voltage boost is maximum when armature mmf and rotor mmf make an angle of
a) zero degrees
b) 45 degrees
c) 90 degrees
d) 180 degrees

View Answer

Answer: a [Reason:] To obtain a maximum of the voltage in induction regulator, the stator mmf and rotor mmf should be stationary and aligned to each other.

10. An alternator is to be used for generation purpose in an aircraft. The most suited operating frequency of the alternator should be
a) of 400 Hz to remove extra bulk
b) of 400 Hz to reduce losses
c) of 50 Hz to remove extra bulk
d) none of the mentioned

View Answer

Answer: a [Reason:] The components to be used in aircrafts are made to operate at very high frequencies so that the size of the components to be used is reduced.

11. A 3-phase synchronous alternator is connected to the infinite bus is over excited, which corresponds to
a) capacitor
b) inductor
c) variable inductor
d) any of the mentioned

View Answer

Answer: a [Reason:] As the machine is over excited, it will act as source of reactive power and it is positive. Q=V (Ecos (delta)-V)/X.

Set 4

1. Refer the diagram; a single-phase supply of 100V, 50Hz is fed to the step-up transformer having primary impedance of 1 ohms and secondary impedance 20 ohms. What is the power consumed by the load of 5 ohms
electrical-machines-questions-answers-machine-ratings-q1
a)20 W
b)40 W
c)10 W
d)100 W

View Answer

Answer: a [Reason:] The referred resistance to the secondary, Z2=1*(5^2) = 25 ohms Total resistance at secondary = 25+20= 45 ohms Total resistance seen by source = 45+5 = 50 ohms Hence, current in secondary = 100/50= 2 A Power consumed by the load = I^2 *R = 4*5= 20 W

2. If the dimension of a single phase transformer is made sqrt(3) times less than the original structure,then what is new no load current rating of the transformer?
a) 1/sqrt(3)
b) sqrt(3)
c) 3
d) 1/3*sqrt(3)

View Answer

Answer: a [Reason:] The no load current of the transformer is directly proportional to the dimension of the transformer.

3. For a single phase, 50 Hz transformer, if the open circuit test is conducted at 40 Hz. What is the variation in the no-load power factor of the transformer?
a) Decreases
b) Increases
c) Remains constant
d) None of the mentioned

View Answer

Answer: a [Reason:] If the frequency reduces then flux density increases, so the flux and then the magnetizing current. When magnetizing current increases power factor angle increases so the power factor decreases.

4. The desired voltage regulation for a single phase, 50 Hz transformer is zero. Its pu ohmic drop is 4% and pu reactive drop is 4%. The required power factor angle for the operation in degrees
a) 45
b) 90
c) 30
d) 60

View Answer

Answer: a [Reason:] The power factor angle is, tan(phi)=pu resistive drop/pu reactive drop = 4/4= 1

5. While conducting lab experiments on DC machine loading, the students are given a machine with its rating as 100 kW maximum rating. Then
a) machine can’t be overloaded after 100 kW
b) machine can be overloaded after 100 kW
c) machine can be overloaded by 5% for a small time duration
d) machine can be overloaded by 10%

View Answer

Answer: a [Reason:] As the maximum rating is specified and operation condition are also same, it cannot be overloaded beyond the maximum.

6. A 3-phase, five limbed shell type transformer, star connected, 200V, 50 Hz, 100 kVA will have
a) no third harmonic current in its phase but has sinusoidal flux
b) third harmonic current in its phase but has flat-topped flux
c) no third harmonic current in its phase but has flat-topped flux
d) third harmonic current in its phase but has sinusoidal flux

View Answer

Answer: a [Reason:] Star connection in three phase has no closed path for the flow of the third harmonic current.

7. For a separately excited dc machine of 25 kW, 250 V and armature resistance of 0.25 ohms, is running at 3000 rpm with supply of 255 V.
The electromagnetic power produced at the armature in kilo watts is
a) 5
b) 10
c) 0.5
d) 8

View Answer

Answer: a [Reason:] The current in armature, Ia = 255-250/0.25 = 20 A Power = Eb*Ia = 250*20 = 5000 W

8. If two alternators A and B are operated in parallel having per unit synchronous reactance as 0.02 ohms and 0.05 ohms respectively.Then what the ratio of contributing loading of machine A to B?
a) 2.5
b) 0.4
c) 1
d) can not be operated in parallel

View Answer

Answer: a [Reason:] The load shared by the alternators is inversely related to their pu reactance.

9. A 200V, 10 hp, 4 poles, 60 Hz, Y-connected induction motor had full load slip of 5%. Then the rotor speed of the motor with respect to stator is
a) 1710 rpm
b) 1800 rpm
c) 90 rpm
d) 3510 rpm

View Answer

Answer: a [Reason:] Synchronous speed, Ns = 120*f/P = 120*60/4 = 1800 rpm Rotor speed = (1-slip)*Ns = 0.95*1800 = 1710 rpm.

10. Auto transformer rating is chosen so as to have best performance, when the analogous two winding transformer has
a) two voltage levels fairly close to each other
b) very high transformation ratio.
c) any voltage levels
d) step down purpose.

View Answer

Answer: a [Reason:] The auto transformer is best suited with the voltage levels of same rating for a two winding transformer.

11. In the lab, two students X and Y conducted the experiments to verify the name plate ratings of the transformer.But student X conducted the same at higher frequency. The kVA reading of student X will be
a) higher than Y’s reading
b) lower than Y’s reading
c) same as Y’s reading
d) none of the mentioned

View Answer

Answer: a [Reason:] As rating is directly proportional to the frequency of operation.

Set 5

1. Assuming the earth to be a sphere of uniform mass density, how much would a body weigh half way down to the centre of the earth if it weighed 250N on the surface?
a) 125N
b) 250N
c) 0N
c) 125N

View Answer

Answer: a [Reason:] Here mg = 250N, d = R/2 Acceleration due to gravity at depth d = R/2, below the earth’s surface will bw gd=g(1-d/R)=g(1-(R/2)/R)=g/2 Therefore, new weight = mgd=mg/2=250/2=125N

2. Calculate the force of attraction between two balls each of mass 1kg when their centres are 10cm apart. The value of gravitational constant G = 6.67×10-11 Nm2 kg(-2).
a) 6.67×10-11N
b) 6.67×10-10N
c) 6.67N
d) 6.67×1010 N

View Answer

Answer: b [Reason:] Force of attraction, F=G (m1 m2)/r2 =(6.67×10-11)×1×1)/0.10=6.67×10-10 N

3. If the kinetic energy of the satellite revolving in an orbit close to the earth’s surface happens to be doubled, what happens to the satellite?
a) It revolves faster
b) It revolves slower
c) It remains unaltered
d) It escapes

View Answer

Answer: d [Reason:] When the kinetic energy of the satellite is doubled, its orbital velocity increases √2 times and becomes equal to the escape velocity. So the satellite will escape.

4. The escape velocity in earth is 11.2km/s. What will be its value on a planet whose radius is double the radius of the earth and eight times the mass of the earth?
a) 22.2km/s
b) 22.4km/s
c) 12km/s
d) 24.2km/s

View Answer

Answer: b [Reason:] vp/ve =√((2GMp)/Rp )×√(Rg/(2GMe ))=√(Mp/Me ×Re/Rp ) vp/ve =√(8×1/2)=2 vp=2ve=2×11.2=22.4km/s

5. A spring balance is suspended from inside an artificial satellite revolving around the earth. If a body of mass 1kg is suspended from it, what would be its reading?
a) 1
b) 2
c) Depends on the mass of the satellite
d) 0

View Answer

Answer: d [Reason:] If a body of mass 1 kg is suspended from a spring balance inside an artificial satellite revolving around the earth, its reading will be zero. This is because the satellite is in a state of free fall.

6. Statement 1- The earth is slowing down and as a result, the moon is coming nearer to it
Statement 2- The angular momentum of the system is not conserved
a) Statement 1 and statement 2 are correct and statement 2 is the correct explanation of statement 1
b) Statement 1 and statement 2 are correct but statement 2 is not the correct explanation of statement 1
c) Statement 1 is true but statement 2 is false
d) Both statement 1 and 2 are false

View Answer

Answer: d [Reason:] Both the statements are false. The earth is not slowing down. The speed of rotation of the earth about its axis remains constant. Further, the angular momentum of the earth-moon system is conserved.

7. Statement 1- If a pendulum falls freely, then its time period is infinite
Statement 2- Free falling body has acceleration equal to g
a) Statement 1 and statement 2 are correct and statement 2 is the correct explanation of statement 1
b) Statement 1 and statement 2 are correct but statement 2 is not the correct explanation of statement 1
c) Statement 1 is true but statement 2 is false
d) Both statement 1 and 2 are false

View Answer

Answer: b [Reason:] Both the assertion and reason are true, but the reason is not the correct explanation of the assertion.

8. Imagine a new planet having the same density as that of earth but it is 3 times bigger than the earth in its size. If the acceleration due to gravity on the surface of the earth is g and that on the surface of the new planet is g, then
a) g=g/9
b) g=27g
c) g=9g
d) g=3g

View Answer

Answer: d [Reason:] g=4/3 πGRρ g=4/3 πGRp ρ=4/3 πG×3R×ρ g=3g

9. A ball dropped from a spacecraft is revolving around the earth at a height of 120km. What will happen to the ball?
a) It will fall down to the earth gradually
b) It will go very far in the space
c) It will continue to move with the same speed along the original orbit of the spacecraft
d) It will move with the same speed, tangentially to the spacecraft

View Answer

Answer: c [Reason:] As no external torque is being applies, by the law of conservation of angular momentum, the ball will continue to move with the same angular velocity along the original orbit of the spacecraft.

10. G is called gravitation constant. True or false?
a) True
b) False

View Answer

Answer: a [Reason:] G is called gravitation constant because the value of G is same for any pair of the bodies in the universe. It does not depend on the nature of the medium between the two bodies or on the nature of the bodies themselves.

11. What is the ration of the force of attraction between two bodies kept in air and the same distance apart in water?
a) 2:1
b) 1:2
c) 1:1
d) 2:4

View Answer

Answer: c [Reason:] The ratio of force of attraction between two bodies kept in air and the same distance apart in water is 1:1, because the gravitational force does not depend on the nature of the medium.