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# Multiple choice question for engineering

## Set 1

1. A conditionally stable system exhibits poor stability at :
a) Low frequencies
b) Reduced values of open loop gain
c) Increased values of open loop gain
d) High frequencies

Answer: b [Reason:] A conditionally stable system is the system which is stable only for certain values of K and exhibits poor stability at the reduced values of open loop gain.

2. The type 0 system has ______ at the origin.
a) No pole
b) Net pole
c) Simple pole
d) Two poles

Answer: a [Reason:] The type of the system is defined as the property of the system which has pole at the origin.

3. The type 1 system has ______ at the origin.
a) No pole
b) Net pole
c) Simple pole
d) Two poles

Answer: c [Reason:] The type of the system is defined as the pole at the zero and type 1 is defined as the 1 pole at the origin.

4. The type 2 system has at the origin.
a) No net pole
b) Net pole
c) Simple pole
d) Two poles

Answer: d [Reason:] Type of the system is defined as the number of pole at origin and type 2 is the 2 poles at the origin.

5. The position and velocity errors of a type-2 system are :
a) Constant, constant
b) Constant, infinity
c) Zero, constant
d) Zero, zero

Answer: c [Reason:] The position and velocity error of the type 2 system is zero and a constant value as for type 2 system velocity error is finite while acceleration error is infinite.

6. Velocity error constant of a system is measured when the input to the system is unit _______ function.
a) Parabolic
b) Ramp
c) Impulse
d) Step

Answer: b [Reason:] Velocity error constant of a system is measured when the input to the system is unit ramp function then only velocity error is finite but error due to other inputs are not defined.

7. In case of type-1 system steady state acceleration is :
a) Unity
b) Infinity
c) Zero
d) 10

Answer: b [Reason:] In case of type-1 system steady state acceleration is infinity as for the type less than 3 acceleration is not defined it is infinity.

8. If a step function is applied to the input of a system and the output remains below a certain level for all the time, the system is :
a) Not necessarily stable
b) Stable
c) Unstable
d) Always unstable

Answer: a [Reason:] If the input is bounded and output is also bounded then the system is always stable and step input is bounded and the output is always under certain li its then the system is stable.

9. Which of the following is the best method for determining the stability and transient response?
a) Root locus
b) Bode plot
c) Nyquist plot
d) None of the mentioned

Answer: a [Reason:] Root locus is the best method for determining stability of the transient response as it gives the exact pole zero location and also their effect on the response.

10. Phase margin of a system is used to specify which of the following?
a) Frequency response
b) Absolute stability
c) Relative
d) Conditional stability

Answer: b: [Reason:] Phase margin of the system can be used for determining the absolute stability of the system.

## Set 2

1. If the performance index of a phase lead compensator is (s+a)/ (s+b) and that of a lag compensator is (s+p)/(s+q), then which one of the following sets of conditions must be satisfied?
a) a>b and p<q
b) a>b and p<q
c) a<b and p<q
d) a<b and p>q

Answer: d [Reason:] In phase lead compensator, zero is nearer to origin. In phase lag compensator, pole is nearer to origin.

2. The compensator Gc(s) =5(1+0.3s)/(1+0.1s) would provide a maximum phase shift of:
a) 20°
b) 45°
c) 30°
d) 60°

Answer: c [Reason:] Maximum phase shift sin^(-1)⁡ [(1-α)/(1+α)] and sin^(-1)⁡[1/2] = 30°.

3. The industrial controller having the best steady-state accuracy is:
a) A derivative controller
b) An integral controller
c) A rate feedback controller
d) A proportional controller

Answer: a [Reason:] The best steady state accuracy is of derivative controller and this is due to the fact that derivative controller is only affected by the steady state response not the transient response.

4. Assertion (A): An on-off controller gives rise to self-sustained oscillation in output.
Reason (R): Location of a pair of poles on the imaginary axis gives to self-sustained oscillation is output.
a) Both A and R true and R is correct explanation of A
b) Both A and R are true but R is not correct explanation of A
c) A is true and R is False
d) A is False and R is True

Answer: a [Reason:] An off-off controller is the initial version of the proportional controller and it gives the self-sustained oscillations and location of poles on the imaginary axis gives the self-sustained oscillations.

5. Consider the following statement:
A proportional plus derivative controller
1. Has high sensitivity
2. Increases the stability of the system
3. Improves the steady state accuracy

Which of these statements are correct?
a) 1,2 and 3
b) 1 and 2
c) 2 and 3
d) 1 and 3

Answer: b [Reason:] A proportional plus derivative controller has the following features as it adds open loop zero on the negative real axis, peak overshoot decreases, bandwidth increases and rise time decreases.

6. Which one of the following compensation is required for improving the transient response of the system?
b) Phase lag compensation
c) Gain compensation
d) Both phase lag compensation and gain compensation

Answer: a [Reason:] For increasing or improving the transient response derivative controller is used and which is the phase lead compensation.

7. Pneumatic controller are :
a) Flexible operation
b) High torque high speed operation
c) Fire and explosion proof operation
d) No leakage

Answer: c [Reason:] Pneumatic controllers are fire and explosion proof operation as they require air and gas fuel for its operation.

8. Hydraulic controller :
a) Flexible operation
b) High torque high speed operation
c) Fire and explosion proof operation
d) No leakage

Answer: b [Reason:] Hydraulic controller must have no leakage and also it requires high torque and high speed operation due to high density of the controller.

9. Electronic Controller :
a) Flexible operation
b) High torque high speed operation
c) Fire and explosion proof operation
d) No leakage

Answer: a [Reason:] Flexible in all sense as it does not require heavy components or extra torque or high speed operations.

10. A plant controlled by a proportional controller. If a time delay element is introduced in the loop its :
a) Phase margin remains the same
b) Phase margin increases
c) Phase margin decreases
d) Gain margin increases

Answer: c [Reason:] The introduction of a time delay element decreases both the phase and gain margin.

## Set 3

1. Fluid power circuits use schematic drawings to:
a) Simplify component function details
b) Make it so only trained persons can understand the functions
c) Make the drawing look impressive
d) Make untrained person to understand

Answer: a [Reason:] Blueprint of any structure is the model that replicates the functions of the original model makes the functional details easy to understand.

2. A pneumatic symbol is:
a) Different from a hydraulic symbol used for the same function
b) The same as a hydraulic symbol used for the same function
c) Not to be compared to a hydraulic symbol used for the same function
d) None of the mentioned

Answer: a [Reason:] The representation for hydraulic and pneumatic systems are different and for creating the easy readability and symbols for both used for the same function.

3. Pneumatic systems usually do not exceed:
a) 1 hp
b) 1 to 2 hp
c) 2 to 3 hp
d) 4 to 5 hp

Answer: a [Reason:] Pneumatic system are the systems in which the control action is mainly controlling the flow of air and mostly do not exceed 1 hp where hp is the horse power unit of power.

4. Most hydraulic circuits:
a) Operate from a central hydraulic power unit
b) Use air-over-oil power units
c) Have a dedicated power unit
d) Does not have dedicated power unit

Answer: a [Reason:] Hydraulic circuits are the circuits where the operation involves conversion of the hydel power into the electrical energy so that it can be stored and used and these operate from a central hydraulic power unit.

5. Hydraulic and pneumatic circuits:
a) Perform the same way for all functions
b) Perform differently for all functions
c) Perform the same with some exceptions
d) Does not perform all the functions

Answer: c [Reason:] Both circuits hydraulic and pneumatic are similar in functionalities and complexities but pneumatic are preferred over hydraulic as pneumatic systems are cleaner.

6. The lubricator in a pneumatic circuit is the:
a) First element in line
b) Second element in line
c) Last element in line
d) Third element in line

Answer: c [Reason:] The lubricator is the fluid that is used to lubricate the parts of the pneumatic circuits to reduce the friction and lubricator in a pneumatic circuit is the last element.

7. Series circuits work on both hydraulic and pneumatic actuators.
a) True
b) False

Answer: b [Reason:] Series circuits are the circuits that in which the elements are connected in series and do not work on both hydraulic and pneumatic actuators.

8. When comparing first cost of hydraulic systems to pneumatic systems, generally they are:
a) More expensive to purchase
b) Less expensive to purchase
c) Cost is same
d) Cost is not required

Answer: b [Reason:] Operating cost that is the cost of the operating or using it practically in daily life and operating cost of hydraulic systems to pneumatic systems is less.

9. When comparing operating cost of hydraulic systems to pneumatic systems, generally they are.
a) More expensive to operate
b) Less expensive to operate
c) Cost is same to operate
d) Cost is not required

Answer: b [Reason:] Operating cost that is the cost of the operating or using it practically in daily life and operating cost of hydraulic systems to pneumatic systems is less.

10. The most common hydraulic fluid is:
a) Mineral oil
b) Synthetic fluid
c) Water
d) Gel

Answer: c [Reason:] Hydraulic fluid is the fluid that is causing conversion process and used in control action which is chemically inert and readily available.

## Set 4

1. The constant M circle for M=1 is the
a) straight line x=-1/2
b) critical point (-1j0)
c) circle with r= 0.33
d) circle with r=0.67

Answer: a [Reason:] For M =1 the constant M circle is a straight line at x=-1/2.

2. The polar plot of a transfer function passes through the critical point (-1,0). Gain margin is
a) Zero
b) -1dB
c) 1dB
d) Infinity

Answer: a [Reason:] Gain margin of a polar plot passing through the critical point is zero.

3. Consider the following statements:
1. The effect of feedback is to reduce the system error
2. Feedback increases the gain of the system in one frequency range but decreases in another
3. Feedback can cause a system that is originally stable to become unstable
Which of these statements are correct.
a) 1,2 and 3
b) 1 and 2
c) 2 and 3
d) 1 and 3

Answer: c [Reason:] Feedback can cause the increase in gain and also can cause stable system to become unstable.

4. The open loop transfer function of a system is G(s) H(s)= K / (1+s)(1+2s)(1+3s)
The phase cross over frequency ωc is
a) V2
b) 1
c) Zero
d) V3

Answer: b [Reason:] Phase crossover frequency is calculated as by calculating the magnitude of the transfer function and equating it to 1 and the frequency calculated at this magnitude is phase cross over frequency.

5. If the gain of the open-loop system is doubled, the gain margin
a) Is not affected
b) Gets doubled
c) Becomes half
d) Becomes one-fourth

Answer: a [Reason:] If the gain of the open-loop system is doubled, the gain margin gets doubled.

6. The unit circle of the Nyquist plot transforms into 0dB line of the amplitude plot of the Bode diagram at
a) 0 frequency
b) Low frequency
c) High frequency
d) Any frequency

Answer: d [Reason:] The unit circle of the Nyquist plot transforms into 0dB line of the amplitude plot of the Bode diagram at any frequency.

7. Consider the following statements:
The gain margin and phase margin of an unstable system may respectively be
1. Positive, positive
2. Positive, negative
3. Negative, positive
4. Negative, negative
Of these statements

a) 1 and 4 are correct
b) 1 and 2 are correct
c) 1, 2 and 3 are correct
d) 2,3 and 4 are correct

Answer: d [Reason:] For unstable system the signs of gain margin and phase margin are always different or they can both be negative.

8. If a system has an open loop transfer function
1-s / 1+s, then the gain of the system at frequency of 1 rad/s will be
a) 1
b) 1/2
c) Zero
d) -1

Answer: d [Reason:] The system is all pass system and the gain of the system at frequency of 1 rad/sec.

9. The polar plot of the open loop transfer function of a feedback control system intersects the real axis at -2. The gain margin of the system is
a) -5dB
b) 0dB
c) -6dB
d) 40dB

Answer: c [Reason:] Gain margin of the system is inverse of the intersect on the real axis and calculated in decibels. G(s) = 1+s / s(1+0.5s).

10. The corner frequencies are
a) 0 and 1
b) 0 and 2
c) 0 and 1
d) 1 and 2

Answer: d [Reason:] Corner frequency can be calculated by time constant form of the transfer function and here the corner frequencies are 1 and 2.

11. For the transfer function
G(s) H(s) = 1 / s(s+1) (s+0.5), the phase cross-over frequency is

Answer: b [Reason:] Phase cross over frequency is calculated at the point where magnitude of the polar plot is 1.

12. The gain margin (in dB) of a system having the loop transfer function
G(s) H(s) = 2 / s(s+1) is
a) 0
b) 3
c) 6
d) 8

Answer: d [Reason:] Gain margin of a system is calculated at the phase cross over frequency and expressed in decibels.

13. The gain margin for the system with open loop transfer function
G(s) H(s) = G(s) =2(1+s) / s2 is
a) 8
b) 0
c) 1
d) -8

Answer: 0 [Reason:] Gain margin of a system is calculated at the phase cross over frequency and expressed in decibels.

14. Statement 1: In constant M circles, as M increases from 1 to 8 radius of circle increases from 0 to 8 and Centre shifts from (-1,0) to (-8,0)
Statement 2: The circle intersects real axis at point (-1/2, 0)
a) Statement 1 is TRUE, 2 is FALSE
b) Statement 1 is FALSE, 2 is TRUE
c) Statement 1 & 2 TRUE
d) Statement 1 & 2 FALSE

Answer: d [Reason:] All the circles pass through the points (0,0) and (-1,0).

## Set 5

1. Assertion (A): The zeroes on the real axis near the origin are generally avoided in design.
Reason (R): In a sluggish system introduction of zeroes can improve the transient response
a) Both A and R are true and R is 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:] Zero is defined as the root of the numerator of the transfer function and zero is to introduce a pronounced peak to the system’s response whereby the peak overshoot may increase appreciably.

2. Addition of zero increases the stability.
a) True
b) False

Answer: a [Reason:] Zero is defined as the root of the numerator of the transfer function and addition of zeroes increases the stability as the speed of response increases.

3. Zeroes are defined as:
a) Roots of the denominator of the closed loop transfer function
b) Roots of the numerator of the closed loop transfer function
c) Parts of the numerator
d) Parts of the denominator

Answer: b [Reason:] Zeroes are the roots of the numerator of the closed loop system and addition of the zeroes increases the stability of the closed loop system.

4. As zero moves sufficiently left from the origin the effect of zero becomes less pronounced.
a) True
b) False

Answer: a [Reason:] The effect of zero on transient response will be negligible if the zero moves left from the origin as the zero which is nearer to the origin is more dominant.

5. If number of poles are greater than number of zeroes then the system is known as ______________
a) Stable system
b) Unstable system
c) Minimum phase system
d) Non-minimum phase system

Answer: c [Reason:] Minimum phase system is defined as the perfect system with zeroes greater than poles and also the zeroes and poles lying on the left half of the s plane entirely.

6. A control system is generally met with the time response specifications:
b) Damping factor
c) Setting time
d) All of the mentioned

Answer: d [Reason:] Steady state error, damping factor and settling times are the specifications are needed to control the system’s stability and speed of response.

7. Steady state accuracy specified in terms of:
b) Damping ratio
c) Natural frequency
d) All of the mentioned

Answer: a [Reason:] Steady state accuracy entirely depends on the accuracy of steady state which is determined by steady state error which is the difference between the final output and desired output.

8. Steady state accuracy is determined by suitable choice of____________
b) Error constants
c) Damping
d) Transient error

Answer: b [Reason:] Steady state accuracy is determined by suitable choice of error constants Kv, Kp and Ka depending upon the type of the system.

9. Damping factor specifies:
a) Peak overshot to step input.
c) Damping ratio
d) Natural frequency