# Multiple choice question for engineering

## Set 1

1. Unit step response of the system described by the equation y(n) +y(n-1) =x(n) is:

a) z^{2}/(z+1)(z-1)

b) z/(z+1)(z-1)

c) z+1/z-1

d) z(z-1)/z+1

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2. Inverse z-transform of the system can be calculated using:

a) Partial fraction method

b) Long division method

c) Basic formula of the z-transform

d) All of the mentioned

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3. Assertion (A): The system function

H(z) = z^{3}-2z^{2}+z/z^{2}+1/4z+1/s is not causal

Reason (R): If the numerator of H (z) is of lower order than the denominator, the system may be causal.

a) Both A and R are true and R is correct explanation of A

b) Both A and R are true and R is not correct Explanation of A

c) A is True and R is false

d) A is False and R is true

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4. Assertion (A): Z-transform is used to analyze discrete time systems and it is also called pulsed transfer function approach.

Reason(R): The sampled signal is assumed to be a train of impulses whose strengths, or areas, are equal to the continuous time signal at the sampling instants.

a) Both A and R are true and R is correct explanation of A

b) Both A and R are true and R is not correct Explanation of A

c) A is True and R is false

d) A is False and R is true

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5. The z-transform corresponding to the Laplace transform G(s) =10/s(s+5) is

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6. Homogeneous solution of: y(n) -9/16y(n-2) = x(n-1)

a) C1(3/4)^{n}+C2(3/4)^{-n}

b) C1-(3/4)^{n-1}+C2(3/4)^{n-1}

c) C1(3/4)^{n}

d) C1-(3/4)^{n}

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7. If the z transform of x(n) is X(z) =z(8z-7)/4z^{2}-7z+3, then the final value theorem is :

a) 1

b) 2

c) ∞

d) 0

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8. Final value theorem is used for:

a) All type of systems

b) Stable systems

c) Unstable systems

d) Marginally stable systems

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9. If the z-transform of the system is given by

H (z) = a+z^{-1}/1+az^{-1}

Where a is real valued:

a) A low pass filter

b) A high pass filter

c) An all pass filter

d) A bandpass filter

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10. The system is stable if the pole of the z-transform lies inside the unit circle

a) True

b) False

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## Set 2

1. A proportional controller leads to:

a) Zero steady state error for step input for type 1 system

b) Zero steady state error for step input for type 0 system

c) Infinite steady state error for step input for a type 1 system

d) Finite steady state error for step input for type 1 system

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2. An all-pass network imparts only

a) Negative phase to the input

b) Positive phase to the input

c) 90 degree phase shift to the input

d) 180 degree phase shift to the input

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3. Which of the following is an effect of lag compensation?

a) Decrease bandwidth

b) Improves transient response

c) Increases the effect of noise

d) Increases stability margin

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4. PD controller:

a) Decreases steady state error and improves stability

b) Rise time decreases

c) Transient response becomes poorer

d) Increases steady state error

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5. PID controller:

a) Decreases steady state error and improves stability

b) Rise time decreases

c) Transient response becomes poorer

d) Increases steady state error

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6. PI controller:

a) Decreases steady state error and improves stability

b) Rise time decreases

c) Transient response becomes poorer

d) Increases steady state error

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7. Proportional controller

a) Decreases steady state error and improves stability

b) Rise time decreases

c) Transient response becomes poorer

d) Increases steady state error

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8. PD controller is used to compensate a system, Compared to the uncompensated system, the compensated system has:

a) A higher type number

b) Reduced damping

c) Higher noise amplification

d) Large transient overshoot

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9. Lead compensator increases bandwidth

a) True

b) False

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10. Lag compensator reduces__________

a) Position constant

b) Velocity constant

c) Position variable

d) Acceleration constant

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## Set 3

1. Closed loop frequency response is very useful as :

a) It approximately predicts the time response of the systems

b) Time response are converted into time domain specifications

c) After design time domain specification is converted into frequency domain

d) All of the mentioned

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2. Maximum peak overshoot in time domain corresponds to :

a) Resonance peak

b) Resonant frequency

c) Bandwidth

d) Cut-off rate

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3. Frequency of oscillation in time domain correspond to :

a) Resonance peak

b) Resonant frequency

c) Bandwidth

d) Cut-off rate

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4. Bandwidth is :

a) Range of frequencies for which the system gain is more than-3dB

b) This is considered good range for transmission of signals

c) For better communication bandwidth of signal must be less

d) All of the mentioned

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5. Cut-off rate is the ability of the system to distinguish the signal from _____________

a) Bandwidth

b) Noise

c) Resonance peak

d) Magnitude

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6. The important figures of merit to the system in frequency domain are :

a) Maximum value of resonant peak

b) Value of resonance frequency

c) Maximum value of resonant peak and Value of resonance frequency

d) Minimum value of resonance frequency

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7. In q(s) plane Nyquist plot is symmetrical about the :

a) Imaginary axis

b) Real axis

c) Origin

d) None of the mentioned

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8. A polar plot intersects the unit circle at a point making -45° to the negative real axis then the phase margin of the system is :

a) -45°

b) 45°

c) 180°-45°

d) 180°+45°

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9. The parameter which is constant along the constant N circle :

a) Frequency

b) Phase angle

c) Magnitude

d) Open loop gain

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10. In second order system gain margin is :

a) Zero value

b) Finite value

c) Infinite value

d) None of the mentioned

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## Set 4

1. The term backlash is associated with:

a) Servomotors

b) Induction relays

c) Gear trains

d) Tacho generator.

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2. With feedback _____ increases.

a) System stability

b) Sensitivity

c) Gain

d) Effects of disturbing signals

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3. By which of the following the system response can be tested better?

a) Ramp input signal

b) Sinusoidal input signal

c) Unit impulse input signal

d) Exponentially decaying signal

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4. In a system zero initial condition means that :

a) The system is at rest and no energy is stored in any of its components

b) The system is working with zero stored energy

c) The system is working with zero reference signal

d) Laplace transform is not possible

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5. In a system low friction co-efficient facilitates:

a) Reduced velocity lag error

b) Increased velocity lag error

c) Increased speed of response

d) Reduced time constant of the system

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6. Hydraulic torque transmission system is analog of :

a) Amplidyne set

b) Resistance-capacitance parallel circuit

c) Motor-generator set

d) Any of the mentioned

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7. Spring constant in force-voltage analogy is analogous to?

a) Capacitance

b) Reciprocal of capacitance

c) Current

d) Resistance

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8. The frequency and time domain are related through which of the following?

a) Laplace Transform and Fourier Integral

b) Laplace Transform

c) Fourier Integral

d) Either b or c

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9. An increase in gain, in most systems, leads to:

a) Smaller damping ratio

b) Larger damping ratio

c) Constant damping ratio

d) Zero damping ratio

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10. Static error co-efficient are used as a measure of the effectiveness of closed loop systems for specified ________ input signal.

a) Acceleration

b) Velocity

c) Position

d) All of the mentioned

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## Set 5

1. Assertion (A): The closed loop stability can be determined from the poles of an open loop system and the polar plot of the frequency response.

Reason (R): Unstable system has right half poles.

a) Both A and R are true and R is correct explanation of A

b) Both A and R are true and R is not correct Explanation of A

c) A is True and R is false

d) A is False and R is true

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2. The open loop control transfer function of a unity feedback system is given by :

G(s) =K/(s+2)(s+4)(s^2+6s+25)

Which is the value of K which causes sustained oscillations in the closed loop system?

a) 590

b) 790

c) 990

d) 1190

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3. The characteristic equation of the control system is s^{5}+15s^{4}+85s^{3}+225s^{2}+274s+120=0 . What are the number of roots of the equation which lie to the left of the line s+1 = 0?

a) 2

b) 3

c) 4

d) 5

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4. The characteristic equation of a system is 2s^{5}+s^{4}+4s^{3}+2s^{2}+2s+1=0 . Which one of the following is correct?

a) Stable

b) Marginally stable

c) Unstable

d) Oscillatory

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5. The characteristic equation of a control system is given by s^{5}+s^{4}+2s^{3}+2s^{2}+4s+6=0. The number of the roots of the equation which lie on the right half of s-plane:

a) 0

b) 1

c) 2

d) 3

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6. Which of the following may result in instability problem?

a) Large error

b) High selectivity

c) High gain

d) Noise

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7. For what values of K does the polynomial s^{4}+8s^{3}+24s^{2}+32s+K=0 have roots with zero real parts?

a) 10

b) 20

c) 40

d) 80

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8. How many roots with positive real parts do the equation s^{3}+s^{2}-s+1=0 have?

a) 0

b) 1

c) 2

d) 3

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9. Phase margin is always positive for stable feedback system?

a) True

b) False

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10. In closed loop control system, what is the sensitivity of the gain of the overall system, M to the variation in G?

a) 1/1+GH

b) 1/1+G

c) G/1GH

d) G/1+G