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# Multiple choice question for engineering

## Set 1

1. Regenerative feedback implies feedback with
a) Oscillations
b) Step input
c) Negative sign
d) Positive sign

Answer: d [Reason:] Regenerative feedback that is the positive feedback implies feedback with Positive sign and for complementary root locus is for the regenerative feedback.

2. The output of a feedback control system must be a function of
a) Reference and output
b) Reference and input
c) Input and feedback signal
d) Output and feedback signal

Answer: d [Reason:] The response of the control system is the output of the control system that depends upon the transfer function of the system and feedback system and also upon the input of the system.

3. A control system with excessive noise, is likely to suffer from
a) Saturation in amplifying stages
b) Loss of gain
c) Vibrations
d) Oscillations

Answer: a [Reason:] Noise is defined as the unwnated output due to the input and this is due to the excessive bandwidth and control system with excessive noise is likely to suufer from saturation in amplifying stages.

4. Zero initial condition for a system means
a) Input reference signal is zero
b) Zero stored energy
c) Initial movement of moving parts
d) System is at rest and no energy is stored in any of its components

Answer: d [Reason:] Zero initial condition means that the system is at rest and no energy is stored in any of its component.

5. Transfer function of a system is used to calculate which of the following?
a) The order of the system
b) The time constant
c) The output for any given input

Answer: c [Reason:] Transfer function of a system is that ratio of Laplace output to the Laplace input at zero initial conditions and which is used to calculate the output for any given input.

6. The band width, in a feedback amplifier.
a) Remains unaffected
b) Decreases by the same amount as the gain increase
c) Increases by the same amount as the gain decrease
d) Decreases by the same amount as the gain decrease

Answer: c [Reason:] The bandwidth is defined as the difference in the higher frequency to the input frequency and increase in the bandwidth leads to the noise and in a feedback amplifier increases by the same amount as the gain decreases.

7. On which of the following factors does the sensitivity of a closed loop system to gain changes and load disturbances depend?
a) Frequency
b) Loop gain
c) Forward gain
d) All of the mentioned

Answer: d [Reason:] Sensitivity is defined as the change in the output with respect to the change in the parameter variations and the change in the input and load disturbances depends upon frequency loop gain and forward gain.

8. The transient response, with feedback system,
a) Rises slowly
b) Rises quickly
c) Decays slowly
d) Decays quickly

Answer: d [Reason:] Transient response is the response that is between time t=0 and at any time and behaviors depends upon the value of damping factor and maximum peak overshoot.

9. The second derivative input signals modify which of the following?
a) The time constant of the system
b) Damping of the system
c) The gain of the system
d) The time constant and suppress the oscillations

Answer: d [Reason:] The time constant is the time required to attain the final value of the steady state and the value if less then the speed of response will be more and second derivative input signals modify suppress the oscillations.

## Set 2

1. An automatic apparatus or device that performs functions ordinarily ascribed to humans or operate with what appears to be almost human intelligence is called ________
a) Robot
b) Human
c) Animals
d) Reptiles

Answer: a [Reason:] Robot is an automatic apparatus or device that performs functions ordinarily ascribed to humans or operate with what appears to be almost human intelligence.

2. The laws of Robotics are:
a) A robot may not injure a human being
b) A robot must abbey the order given by human except when conflict with the first law
c) A robot must protect its own existence except when it is violating first and second law
d) Both b and c

Answer: d [Reason:] A robot may not injure a human being or through in action, allow human being to be harmed.

3. The basic components of robot are:
b) Sensors and controllers
c) User interface and power conversion unit
d) All of the mentioned

Answer: d [Reason:] The basic components of robot are the mechanical linkage, sensors and controllers, User interface and power conversion unit.

4. Assertion (A): Degree of freedom is defined as the number of variables to define motion in the body in space.
Reason (R): Maximum degree of freedom can be six in a robot.
a) Both A and R are true and R is not correct explanation of A.
b) Both A and R are true but R is not correct explanation of A.
c) A is true but R is false
d) A is false but R is true

Answer: b [Reason:] Degree of freedom defines the variables responsible for the motion of the robot and allows robot to reach all positions and orientations.

5. A _________ is connection between parts or links in a robot that allow motion.
a) Hinge
b) Joint
c) Dis joint
d) None of the mentioned

Answer: b [Reason:] A joint is connection between parts or links in a robot that allow motion. It has translator and rotatory motion.

6. Classification of Robot is based on:
a) Geometry and geometric classification
b) Left right classification
c) Based on control system
d) All of the mentioned

Answer: d [Reason:] Robots can be classified on the basis of the movement their structure and geometry as humanoid robots and gantry robots.

7. Assertion (A): The control system of an industrial robot determine its flexibility and efficiency, within the limits set beforehand by the design of the mechanical structure.
Reason (R): The control system provides a logical sequence for the robot to follow.
a) Both A and R are true and R is not correct explanation of A.
b) Both A and R are true but R is not correct explanation of A.
c) A is true but R is false
d) A is false but R is true

Answer: a [Reason:] The system provides the theoretical position values for each step and continuously measures the actual position during movement.

8. Hierarchical level control involves :
a) Level 1: Actuator control controls individual robot actuators
b) Level 2: Path control coordinates robot path movement
c) Level 3: Main control high level instruction interpreter
d) All of the mentioned

Answer: d [Reason:] Hierarchy refers to the system where some form of levels are used as higher to lower or vice versa and this level control mainly involves actuator control, path control and main control for various functioning of the parts of the robot.

9. Non servo robots are also called as:
a) Pick and place
b) Fixed stop robot
c) Both of the mentioned
d) None of the mentioned

Answer: c [Reason:] Non servo robots are simplest robots as they are the least complex structures and they are made to do some specific and less jobs and it is an open loop system.

10. Characteristics of non-servo robot are:
a) Relatively inexpensive compared to servo robots
b) Simple, understand and operate
c) Precise and reliable
d) Closed loop system.

Answer: d [Reason:] Non-servo robots are open loop system and less costly and they are less complex and can be used once or twice for some work and they are less reliable.

## Set 3

1. Consider the points s1 =-3+4j and s2 = -3-2j in the s-plane. Then, for a system with the open loop transfer function G(s)H(s) =K/(s+1)4.
a) S1 is on the root locus but s2 is not
b) S2 is on the root locus but s1 is not
c) Both s1 and s2 are not on the root locus
d) Neither s1 nor s2 is on the root locus

Answer: b [Reason:] Roots lying on the root locus which is the locus traced by the gain of the system with respect to the frequency and depends upon the open loop poles and their position.

2. The characteristic equation of a control system is given by s(s+4)(s2+2s+s) +k(s+1) =0. What are the angles of the asymptotes for the root loci
a) 60°, 180°, 300°
b) 0°, 180°, 300°
c) 120°, 180°, 240°
d) 0°, 120°, 240°

Answer: a [Reason:] P-Z = 3 Angle of asymptote = (2q+1)180°/P-Z Hence the angles are 60°, 180°, and 300°.

3. The characteristic equation of a feedback control system is given by s3+5s2+(K+6)s+K=0. In the root loci diagram, the asymptotes of the root loci for large K meet at a point in the s plane whose coordinates are:
a) (2,0)
b) (-1,0)
c) (-2,0)
d) (-3,0)

Answer: c [Reason:] The point of meeting of the asymptotes are is calculated by using Routh Hurwitz table and then equating the S^0 term equal to zero.

4. The root locus diagram has loop transfer function G(s)H(s) = K/ s(s+4)(s2+4s+5) has
a) No breakaway points
b) Three real breakaway points
c) Only one breakaway points
d) One real and two complex breakaway points

Answer: b [Reason:] The breakaway points are the points at which the root locus branches are broken and are calculated by differentiating the value of K with respect to s and equating it with zero.

5. For asymptotes passing from breakaway point then this point is also centroid
a) True
b) False

Answer: a [Reason:] For asymptotes which are the tangents to the root locus and extending from the minus infinite to plus infinite and if passing from breakaway point then this point is also centroid.

6. Transportation lag is seen in systems:
a) Amount to be transferred in large
b) Time take to transfer is large
c) Inefficiency of the process
d) Errors

Answer: b [Reason:] Transportation lag refers to the lag where the output does not follow the input and is seen in systems where the time taken to transfer is very large.

7. Mediums responsible for transportation lag are:
a) Lines
b) Pipes
c) Belt conveyors
d) All of the mentioned

Answer: d [Reason:] Transportation lag is mainly seen in the practical mediums where the time of transfer is very large and accurate results are not possible in these type of the systems.

8. Linear lumped parameter models are not valid under situations as:
a) Transmission pipe between the hydraulic pump and the motor causes a time lag in transportation of oil from pump to motor
b) Transmission of heat by conduction or convection produces serious transportation lag
c) Both of the mentioned
d) None of the mentioned

Answer: c [Reason:] Linear lumped parameter models are the models used in the electrical circuits that are used to store energy and not valid when the pure time lags are negligible compared to other lags in the system.

9. Practically all the systems have transportation lag :
a) True
b) False

Answer: b [Reason:] Not all systems have transportation lag but whose transmission time is more ha the transmission lag and for these type of the systems the output is not accurate.

10. Transportation lag causes :
a) Instability in system
b) Stability in system
c) System remains unaffected
d) Bandwidth increases

Answer: a [Reason:] Transportation lag is the delay in the generation of the output where for the input given output is not present and causes instability in the system.

## Set 4

1. I. Core flux – Depends on applied voltage
II. Leakage flux – Depends on winding current
Which of the above two are not matched correctly?
a) I
b) II
c) I,II
d) none of the mentioned

Answer: d [Reason:] Both the statements are correct, as the leakage flux depends on the current flowing in the respective winding and the core flux depends on the voltage.

2. CRGO Laminations in a transformer are used to minimize
a) eddy current loss
b) hysteresis loss
c) both eddy current and hysteresis loss
d) ohmic loss

Answer: c [Reason:] CRGO steel is rolled grain type domains which not only help for faster reversals but also the reduction of eddy current losses.

3. A single phase transformer has emf per turn having 2310/220 V, 50Hz transformer as 13 V. Then the estimated primary turns will be
a) 189 turns
b) 179 turns
c) 176 turns
d) 190 turns

Answer: a [Reason:] N2 = Total secondary voltage/Emf per turn = 220/13 = 16.92 = 17(approx) For N2 = 17, N1 = 178.5. But it is not an integer, so this approximation is wrong. If N2 = 18, N1=189 turns.

4. A single phase transformer has emf per turn having 2310/220 V, 50Hz transformer as 13 V. The core area is(in square cm)
a) 393
b) 277.8
c) 358.92
d) 450.03

Answer: a [Reason:] Emf per turn = 1.44*f*flux density * Area*N2 Area = 220/(18*1.44*50*1.4) = 393 sq.cm.

5. If a transformer is fed from a dc rather than a 1-phase ac supply, then the transformer will
a) burn its windings
b) operate normal
c) will not operate
d) will give very small leakage flux

Answer: a [Reason:] Dc is nothing but ac at zero frequency. So the reactance will be zero and the current will be limited solely by the small resistance of the winding which will produce very high amount of current to flow through the windings, so burning them up.

6. For a single phase transformer operating at normal operating conditions has useful flux of 1 Wb. If the machine is loaded at 0.8 p.f., then its mutual
flux
a) may decrease to 0.98 Wb
b) remains constant
c) may increase 1.02 Wb
d) may decrease to 0.8 Wb

Answer: a [Reason:] The mutual flux will decrease by a very small amount.

7. The flux involved in the emf equation of a transformer has
a) rms value
b) average value
c) total value
d) maximum value

Answer: d [Reason:] The flux is always taken at its peak in the practical calculation cases.

8. If the frequency at the primary supply is varied gradually, then the secondary terminal voltage will
a) not change
b) vary directly
c) will vary oppositely
d) will vary inverse of frequency

Answer: a [Reason:] The changes in the frequency is not reflected due to the flux density variation correspondingly.

9. There are two identical transformers A and B such that flux density applied to B is doubled.
Then magnetizing current of B is
a) larger than A
b) double of A
c) half of A
d) same as that of A.

Answer: a [Reason:] When we double the flux density, as per the magnetization curve of the core, the magnetizing current is much larger than double of the machine A.

10. A 20KVA, 2200/220 V, 50 Hz single phase transformer has the below parameters:
HV : r = 2.4 ‎Ω, X=6 ‎Ω
LV: r = 0.03 ‎Ω, X = 0.07 ‎Ω
The primary reactance referred to secondary is
a) 0.024 ‎Ω
b) 0.06 ‎Ω
c) 3 ‎Ω
d) 7 ‎Ω

Answer: b [Reason:] Primary reactance referred to secondary = x1*(N2/N1)^2 = 6*(220/2200)^2 = 0.06 ‎Ω.

11. A 20KVA, 2200/220 V, 50 Hz single phase transformer has the below parameters:
HV : r = 2.4 ‎Ω, X=6 ‎Ω, Primary
LV: r = 0.03 ‎Ω, X = 0.07 ‎Ω, Secondary
The secondary reactance referred to primary is
a) 0.024 ‎Ω
b) 0.06 ‎Ω
c) 3 ‎Ω
d) 7 ‎Ω

Answer: d [Reason:] Secondary reactance referred to primary = x2*(N1/N2)^2 = 0.07*(2200/220)^2 = 7.0 Ω

12. A 20KVA, 2200/220 V, 50 Hz single phase transformer has the below parameters:
HV : r = 2.4 ‎Ω, X=6 ‎Ω
LV: r = 0.03 ‎Ω, X = 0.07 ‎Ω
The primary resistance referred to secondary is
a) 0.024 ‎Ω
b) 0.06 ‎Ω
c) 3 ‎Ω
d) 7 ‎Ω

Answer: a [Reason:] Primary resistance referred to secondary = r1*(N2/N1)^2 = 2.4*(220/2200)^2 = 0.024 ‎Ω.

13. A 20KVA, 2200/220 V, 50 Hz single phase transformer has the below parameters:
HV : r = 2.4 ‎Ω, X=6 ‎Ω
LV: r = 0.03 ‎Ω, X = 0.07 ‎Ω
The secondary resistance referred to primary is
a) 0.024 ‎Ω
b) 0.06 ‎Ω
c) 3 ‎Ω
d) 7 ‎Ω

Answer: c [Reason:] Secondary resistance referred to primary = r2*(N1/N2)^2 = 0.03*(2200/220)^2 = 3.0 Ω.

14. In a transformer ______ decreases with increase of the leakage flux.
a) secondary terminal voltage
b) secondary induced voltage
c) primary induced voltage
d) all of the mentioned

Answer: a [Reason:] The leakage is modelled as the reactance which incurrs as a loss to the terminal voltage not the induced voltage.

15. The components needed to draw the phasor diagram of the transformer is
a) A,B,C
b) B
c) B,C
d) A,B

Answer: a [Reason:] All the mentioned quantities are must to draw the phasor diagram of a transformer.

16. In a transformer if the frequency of the supply is varied then the magnetizing current in the core also varies.
a) True
b) False

Answer: b [Reason:] The magnetizing current does not depend on the frequency of the supply fed to it.

## Set 5

1. A 3 phase synchronous machine is _________ excited machine.
a) doubly
b) single
c) two stage
d) feedback based

Answer: a [Reason:] The 3 phase synchronous machine has two excitations. Ac excitation at armature while dc excitation at field winding.

2. Field winding of a dc machine
a) always absorbs power
b) absorbs real power at lagging load
c) delivers power while behaving as generator
d) always delivers power

Answer: a [Reason:] Field is always given supply from dc system so it always absorbs power as it is necessary to produce the flux.

3. In large synchronous machine, field winding is placed on ______ and ac supply on ______
a) rotor, stator
b) stator, rotor
c) armature, slots
d) pole shoes, stator

Answer: a [Reason:] The field winding is placed on the stator as it will carry less current while the ac supply is fed at stator as it will have to carry large amount of current.

4. The pilot exciter in dc exciters is ________
a) dc shunt generator feeding field winding of mains
b) universal motor
c) stepper motor feeding the field winding of mains
d) any of the mentioned

Answer: a [Reason:] Pilot exciter is dc shunt generator which supplies the field of main winding.

5. The main problems faced by conventional DC exciters are/is _______
a) cooling and maintainance
b) wear and tear
d) all of the mentioned

Answer: d [Reason:] The conventional dc exciters have all the above mentioned losses which make them out dated and least efficient.

6. The static excitations mainly comprises of _______
a) brushless excitation system
b) thyrister based excitation system
c) synchronous motor excitation system
d) brushless and thyristor based excitation system

Answer: b [Reason:] SCRs are used in the rectifier configuration as a static system for excitation for dc field winding.

7. The excitation system and speed of alternator has _______
a) linear response
b) exponential response
c) rectangular hyperbola response
d) circular response

Answer: a [Reason:] As the excitation energy is directly taken from alternator terminals, excitation voltage is directly proportional to speed.

8. The brushless excitation and conventional DC excitation systems are comparable but one significant change is _______
a) pilot exciter is brushless permanent magnet motor
b) three phase rectifier feeds directly to main exciter
c) a three phase rectifier is fed by main exciter
d) no direct rectification is provided to the pilot exciter

Answer: a [Reason:] The brushless excitation involves a brushless permanent motor which acts as an auxiliary exciter.

9. The main exciter used in DC excitation is ________
a) field on stator
b) armature on stator
c) field on rotor
d) field on poles