# Multiple choice question for engineering

## Set 1

1. Consider the loop transfer function K(s+6)/(s+3)(s+5) In the root locus diagram the centroid will be located at:

a) -4

b) -1

c) -2

d) -3

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2. Which one of the following applications software’s is used to obtain an accurate root locus for?

a) LISP

b) MATLAB

c) dBase

d) Oracle

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3. Which one of the following is not the property of root loci?

a) The root locus is symmetrical about imaginary axis

b) They start from the open loop poles and terminate at the open loop zeroes

c) The breakaway points are determined from dK/ds = 0

d) Segments of the real axis are the part of the root locus if and only is the total number of real poles and zeroes to their right is odd.

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4. The breakaway point calculated mathematically must always lie on the root locus.

a) True

b) False

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5. What is the number of the root locus segments which do not terminate on zeroes?

a) The number of poles

b) The number of zeroes

c) The difference between the number of poles and zeroes

d) The sum of the number of poles and the number of the zeroes

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6. Which one of the following are correct?

The root locus is the path of the roots of the characteristic equation traced out in the s-plane?

a) As the input of the system is changed

b) As the output of the system is changed

c) As a system parameter is changed

d) As the sensitivity is changed

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7. If the gain of the system is reduced to a zero value, the roots of the system in the s-plane,

a) Coincide with zero

b) Move away from zero

c) Move away from poles

d) Coincide with the poles

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8. The addition of open loop zero pulls the root loci towards:

a) The left and therefore system becomes more stable

b) The right and therefore system becomes unstable

c) Imaginary axis and therefore system becomes marginally stable

d) The left and therefore system becomes unstable

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9. If root loci plots of a particular control system do not intersect the imaginary axis at any point, then the gain margin of the system will be:

a) 0

b) 0.707

c) 1

d) Infinite

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10. When the number of poles is equal to the number of zeroes, how many branches of root locus tends towards infinity?

a) 1

b) 2

c) 0

d) Equal to number of zeroes

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## Set 2

1. Routh Hurwitz criterion gives:

a) Number of roots in the right half of the s-plane

b) Value of the roots

c) Number of roots in the left half of the s-plane

d) Number of roots in the top half of the s-plane

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2. Routh Hurwitz criterion cannot be applied when the characteristic equation of the system containing coefficient’s which is/are

a) Exponential function of s

b) Sinusoidal function of s

c) Complex

d) Exponential and sinusoidal function of s and complex

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3. Consider the following statement regarding Routh Hurwitz criterion:

a) It gives absolute stability

b) It gives gain and phase margin

c) It gives the number of roots lying in RHS of the s-plane

d) It gives gain, phase margin and number of roots lying in RHS of the s-plane

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4. The order of the auxiliary polynomial is always:

a) Even

b) Odd

c) May be even or odd

d) None of the mentioned

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5. Which of the test signals are best utilized by the stability analysis.

a) Impulse

b) Step

c) Ramp

d) Parabolic

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6. The characteristic equation of a system is given as3s4+10s3+5s2+2=0. This system is :

a) Stable

b) Marginally stable

c) Unstable

d) Linear

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7. The characteristic equation of a system is given ass3+25s2+10s+50=0. What is the number of the roots in the right half s-plane and the imaginary axis respectively?

a) 1,1

b) 0,0

c) 2,1

d) 1,2

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8. Consider the following statement:

a) A system is said to be stable if its output is bounded for any input

b) A system is said to be stable if all the roots of the characteristic equation lie on the left half of the s plane.

c) A system is said to be stable if all the roots of the characteristic equation have negative real parts.

d) A second order system is always stable for finite values of open loop gain

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9. The necessary condition for the stability of the linear system is that all the coefficients of characteristic equation 1+G(s)H(s) =0, be real and have the :

a) Positive sign

b) Negative sign

c) Same sign

d) Both positive and negative

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10. For making an unstable system stable:

a) Gain of the system should be increased

b) Gain of the system should be decreased

c) The number of zeroes to the loop transfer function should be increased

d) The number of poles to the loop transfer function should be increased

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## Set 3

1. A signal flow graph is the graphical representation of the relationships between the variables of set linear algebraic equations.

a) True

b) False

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2. A node having only outgoing branches.

a) Input node

b) Output node

c) Incoming node

d) Outgoing node

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3. Use mason’s gain formula to find the transfer function of the given signal flow graph:

a) abd/1-(ac)

b) abdeg/1-(bc+ef)+bcef

c) abd/1-(bc+ef)+bcef

d) adcdef/1-(bc+ef)+bcef

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4. Use mason’s gain formula to find the transfer function of the following signal flow graph:

a) abcd+efg/1-cd-fg-cdfg

b) acdfg+bcefg/1-cd-fg-cdfg

c) abef+bcd/1-cd-fg-cdfg

d) adcdefg/1-cd-fg-cdfg

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5. Loop which do not possess any common node are said to be ___________ loops.

a) Forward gain

b) Touching loops

c) Non touching loops

d) Feedback gain

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6. Signal flow graphs:

a) They apply to linear systems

b) The equation obtained may or may not be in the form of cause or effect

c) Arrows are not important in the graph

d) They cannot be converted back to block diagram

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7. Signal flow graphs are reliable to find transfer function than block diagram reduction technique.

a) True

b) False

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8. The relationship between an input and output variable of a signal flow graph is given by the net gain between the input and output node is known as the overall______________

a) Overall gain of the system

b) Stability

c) Bandwidth

d) Speed

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9. Use mason’s gain formula to calculate the transfer function of given figure:

a) G1/1+G2H

b) G1+G2/1+G1H

c) G2/1+G1H

d) None of the mentioned

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10. Use mason’s gain formula to find the transfer function of the given figure:

a) G1+G2

b) G1+G1/1-G1H+G2H

c) G1+G2/1+G1H+G2H

d) G1-G2

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## Set 4

1. Sampling can be done by:

a) Impulse train sampling

b) Natural sampling

c) Flat-top sampling

d) All of the mentioned

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2. The first step required to convert analog signal to digital is :

a) Sampling

b) Holding

c) Reconstruction

d) Quantization

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3. Sampling is necessary :

a) In complex control systems

b) Where high accuracy is required

c) Non automated control systems

d) Automated control system

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4. Sampled data technique is appropriate as:

a) For long distance data transmission

b) Pulses are transferred by little loss of accuracy

c) More than one channel of information is sequentially sampled and transmitted.

d) All of the mentioned

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5. Signal sampling reduces the power demand made on the signal.

a) True

b) False

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6. The use of sampled data control system are:

a) For using analog components as the part of the control loop

b) For time division of control components

c) Whenever a transmission channel forms a part of closed loop

d) None of the mentioned

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7. _______________ is a sampling pattern which is repeated periodically

a) Single order sampling

b) Multi order sampling

c) Zero order sampling

d) Unordered sampling

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8. For the successful reconstruction of signals :

a) Sampling frequency must be equal to the message signal

b) Sampling frequency must be greater to the message signal

c) Sampling frequency must be less to the message signal

d) Sampling frequency must be greater than or equal to the message signal

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9. The signal is reconstructed back with the help of

a) Zero order hold circuits

b) Extrapolations

c) Signal is reconstructed with zero order holds and extrapolations

d) Signal is not reconstructed

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10. Aliasing is caused when:

a) Sampling frequency must be equal to the message signal

b) Sampling frequency must be greater to the message signal

c) Sampling frequency must be less to the message signal

d) Sampling frequency must be greater than or equal to the message signal

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## Set 5

1. Which of the following is an electromechanical device ?

a) Induction relay

b) Thermocouple

c) LVDT

d) Any of the mentioned

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2. A differentiator is usually not a part of a control system because it

a) Reduces damping

b) Reduces the gain margin

c) Increases input noise

d) Increases error

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3. If the gain of the critical damped system is increased it will behave as

a) Oscillatory

b) Critically damped

c) Overdamped

d) Underdamped

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4. In a control system integral error compensation _______ steady state error

a) Increases

b) Minimizes

c) Does not have any effect on

d) All of the mentioned

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5. With feedback _____ reduces.

a) System stability

b) System gain

c) System stability and gain

d) None of the mentioned

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6. 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

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7. Which of the following can be measured by LVDT?

a) Displacement

b) Velocity

c) Acceleration

d) All of the mentioned

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8. ____________directly converts temperature into voltage.

a) Thermocouple

b) Potentiometer

c) Gear train

d) LVDT

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

a) Systems having complexities and non-linearity’s

b) Systems having stability problems

c) Systems having multiple input disturbances

d) All of the mentioned

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

a) Alternating current

b) Direct current

c) A.C. voltage

d) D.C. voltage