# Multiple choice question for engineering

## Set 1

1. Statement (I): Aliasing occurs when the sampling frequency is less than twice the maximum frequency in the signal.

Statement (II): Aliasing is a reversible process.

a) Both statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I).

b) Both Statement (I) and Statement (II) are individually true but Statement (II) is not correct explanation of Statement (I)

c) Statement (I) is true but Statement (II) is false

d) Statement (I) is False but Statement (II) is true

### View Answer

2. A band limited signal with a maximum frequency of 5 KHz to be sampled. According to the sampling theorem, the sampling frequency which is not valid is:

a) 5 KHz

b) 12 KHz

c) 15 KHz

d) 20 KHz

### View Answer

3. Let x(t) be a continuous-time, real valued signal band-limited to F Hz. The Nyquist sampling rate in Hz, For y(t) =x(0.5t) +x(t)-x(2t) is

a) F

b) 2F

c) 4F

d) 8F

### View Answer

4. Increased pulse-width in the flat-top sampling leads to:

a) Attenuation of high frequencies in reproduction

b) Attenuation of low frequencies in reproduction

c) Greater aliasing errors in reproduction

d) No harmful effects in reproduction

### View Answer

5. A bandpass sampling extends from 4-6 kHz. What is the smallest sampling frequency required to retain all the information in the signal.

a) 1 kHz

b) 2 kHz

c) 3 kHz

d) 4 kHz

### View Answer

6. A signal represented by x(t) =5cos 400πt is sampled at a rate 300 samples/sec. The resulting samples are passed through an ideal low pass filter of cut-off frequency 150 Hz. Which of the following will be contained in the output of the LPF?

a) 100 Hz

b) 100 Hz, 150 Hz

c) 50 Hz, 100 Hz

d) 50 Hz, 100 Hz, 150 Hz

### View Answer

7. A signal m(t) with bandwidth 500 Hz is first multiplied by a signal g(t). The resulting signal is passed through an ideal low pass filter with bandwidth 1 kHz. The output of the low pass filter would be :

a) Impulse

b) m(t)

c) 0

d) m(t)del(t)

### View Answer

8. An LTI system having transfer function s^{2}+1/s^{2}+2s+1 and input x(t) =sin(t+1) is in steady state. The output is sampled at ws rad/s to obtain the final output {y (k)}. Which of the following is true?

a) Y is zero for all sampling frequencies ws

b) Y is non zero for all sampling frequencies ws

c) Y is non zero for ws>2 but zero for ws<2

d) Y is zero for ws>2 but non zero for ws<2

### View Answer

^{s}/s

^{2}+1 Y(s) = e

^{s}/s

^{2}+2s+1 Y (∞) =0.

9. A digital measuring instrument employs a sampling rate of 100 samples/second. The sampled input x(n) is averaged using the difference equation:

Y (n) =[x (n)+x (n-1)+x(n-2)+x(n-4)/4]

For a step input, the maximum time taken for the output to reach the final value after the input transition is

a) 20 ms

b) 40 ms

c) 80 ms

d) ∞

### View Answer

10. The sinusoid x(t) =6cos10πt is sampled at the rate of 15 Hz and applied to ideal rectangular LPF with cut-off frequency of 10 Hz, then the output of filter contains:

a) Only 10π rad/sec component

b) 10π rad/sec component

c) 10π rad/sec and 20π rad/sec components

d) +10π rad/sec and +20π rad/sec components

### View Answer

## Set 2

1. First column elements of the Routh’s tabulation are 3, 5, -3/4, ½, 2. It means that there are:

a) Is one root in the left half of s-plane

b) Are two roots in the left half of s-plane

c) Are two roots in the right half of the s-plane

d) Is one root in the right half of s-plane

### View Answer

2. Assertion (A): Feedback control system offer more accurate control over open-loop systems.

Reason (R): The feedback path establishes a link for input and output comparison and subsequent error correction.

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

### View Answer

3. Consider the following statements:

a) The effect of feedback is to reduce the system error

b) Feedback increases the gain of the system in one frequency range but decreases in the other

c) Feedback can cause a system originally stable to become unstable

d) Both a and c

### View Answer

4. The Routh-Hurwitz criterion cannot be applied when the characteristic equation of the system contains any coefficients which is :

a) Negative real and exponential function

b) Negative real, both exponential and sinusoidal function of s

c) Both exponential and sinusoidal function of s

d) Complex, both exponential and sinusoidal function of s

### View Answer

5. The following characteristic equation results in stable operation of the feedback system s^{3}+4s^{2}+10s+11=0

a) True

b) False

### View Answer

6. Consider the following statements:

Routh-Hurwitz criterion gives:

1. Absolute stability

2. The number of roots lying on the right half of the s-plane

3. The gain margin and the phase margin

a) 1,2 and3

b) 1 and 2

c) 2 and 3

d) 1 and 3

### View Answer

7. The given characteristic equation s^{4}+s^{3}+2s^{2}+2s+3=0 has:

a) Zero root in the s-plane

b) One root in the RHS of s-plane

c) Two root in the RHS of s-plane

d) Three root in the RHS of s-plane

### View Answer

8. Which of the following techniques is utilized to determine at the actual point at which the root locus crosses the imaginary axis?

a) Nyquist technique

b) Routh-Hurwitz technique

c) Nichol’s technique

d) Bode technique

### View Answer

9. The characteristic equation of a control system is given by s^{6}+2s^{5}+8s^{4}+12s^{3}+20s^{2}+16s+16=0 . The number of the roots of the equation which lie on the imaginary axis of s-plane:

a) 0

b) 2

c) 4

d) 6

### View Answer

10. Assertion (A): A linear, negative feedback control system is invariable stable if its open loop configuration is stable

Reason (R): the negative feedback reduces the overall gain of the feedback.

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

### View Answer

## Set 3

1. The characteristic equation of a feedback control system is given bys^{3}+5s^{2}+(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)

### View Answer

^{0}term equal to zero.

2. The root locus diagram has loop transfer function G(s)H(s) = K/ s(s+4)(s^{2}+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

### View Answer

3. For asymptotes passing from breakaway point then this point is also centroid

a) True

b) False

### View Answer

4. 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

### View Answer

5. Mediums responsible for transportation lag are:

a) Lines

b) Pipes

c) Belt conveyors

d) All of the mentioned

### View Answer

6. 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) Transmission pipe causes the time lag and loss of heat by conduction and convection

d) Transmission of pipe causes neither any time lag nor any heat loss

### View Answer

7. Practically all the systems have transportation lag :

a) True

b) False

### View Answer

8. Transportation lag causes :

a) Instability in system

b) Stability in system

c) System remains unaffected

d) Bandwidth increases

### View Answer

9. 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

### View Answer

10. 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

### View Answer

## Set 4

1. Stability of a system implies that :

a) Small changes in the system input does not result in large change in system output

b) Small changes in the system parameters does not result in large change in system output

c) Small changes in the initial conditions does not result in large change in system output

d) Small changes in the initial conditions result in large change in system output

### View Answer

2. A linear time invariant system is stable if :

a) System in excited by the bounded input, the output is also bounded

b) In the absence of input output tends zero

c) Both a and b

d) None of the mentioned

### View Answer

3. Asymptotic stability is concerned with :

a) A system under influence of input

b) A system not under influence of input

c) A system under influence of output

d) A system not under influence of output

### View Answer

4. Bounded input and Bounded output stability notion concerns with :

a) A system under influence of input

b) A system not under influence of input

c) A system under influence of output

d) A system not under influence of output

### View Answer

5. If a system is given unbounded input then the system is:

a) Stable

b) Unstable

c) Not defined

d) Linear

### View Answer

6. Linear mathematical model applies to :

a) Linear systems

b) Stable systems

c) Unstable systems

d) All of the mentioned

### View Answer

7. For non-linear systems stability cannot be determined due to:

a) Possible existence of multiple equilibrium states

b) No correspondence between bounded input and bounded output stability and asymptotic stability

c) Output may be bounded for the particular bounded input but may not be bounded for the bounded inputs

d) All of the mentioned

### View Answer

8. If the impulse response in absolutely integrable then the system is :

a) Absolutely stable

b) Unstable

c) Linear

d) None of the mentioned

### View Answer

9. The roots of the transfer function do not have any effect on the stability of the system.

a) True

b) False

### View Answer

10. Roots with higher multiplicity on the imaginary axis makes the system :

a) Absolutely stable

b) Unstable

c) Linear

d) None of the mentioned

### View Answer

## Set 5

1. In a control system integral error compensation _______steady state error

a) Increases

b) Minimizes

c) Does not have any effect on steady state error

d) All of the mentioned

### View Answer

2. With feedback _____ reduces.

a) System stability

b) System gain

c) System stability and gain

d) Damping

### View Answer

3. An amplidyne can give which of the following characteristics?

a) Constant current

b) Constant voltage

c) Constant current as well as constant voltage

d) Constant current, constant voltage and constant power

### View Answer

4. Which of the following cannot be measured by LVDT?

a) Displacement

b) Velocity

c) Acceleration

d) Pressure

### View Answer

5. __________directly converts temperature into voltage.

a) Thermocouple

b) Potentiometer

c) Gear train

d) LVDT

### View Answer

6. The transfer function technique is considered as inadequate under which of the following conditions?

a) Systems having complexities and nonlinearities

b) Systems having stability problems

c) Systems having multiple input disturbances

d) All of the mentioned

### View Answer

7. Which of the following is the output of a thermocouple?

a) Alternating current

b) Direct current

c) A.C. voltage

d) D.C. voltage

### View Answer

8. A.C. servomotor is basically a

a) Universal motor

b) Single phase induction motor

c) Two phase induction motor

d) Three phase induction motor

### View Answer

9. The first order control system, which is well designed, has a

a) Small bandwidth

b) Negative time constant

c) Large negative transfer function pole

d) None of the mentioned

### View Answer

10. Which of the following is exhibited by Root locus diagrams?

a) The poles of the transfer function for a set of parameter values

b) The bandwidth of the system

c) The response of a system to a step input

d) The frequency response of a system