GURU TEGH BAHADUR INSTITUTE OF TECHNOLOGY

(MID TERM EXAMINATION-NOVEMBER 2021)

PAPER TITLE: CONTROL SYSTEMS PAPER CODE: ETEL307

TIME DURATION:60 MINS MAX MARKS:30

ALL QUESTIONS CARRY ONE MARK EACH

Q1. Which of the following can be used as a tacho generator in control systems?
a)Magnetic Amplifier
b) Microsyn
c) DC servomotor
d) AC servomotor

Q2.Consider the following statements with respect to the feedback of the control systems.
i. Feedback can improve stability or be harmful to stability if it is not properly applied.
ii. Feedback can always improve stability
iii. In many situations the feedback can reduce the effect of noise and disturbance on system
performance.
iv. In general the sensitivity of the system gain of a feedback system of a parameter variation depends
on where the parameter is located.
a) i, ii, iii and iv only
b) i, ii and iii only
c) i, iii and iv only
d) i, ii and iv only

Q3. Use mason’s gain formula to find the transfer function of the following signal flow graph:

a) acdfg+bcefg/1-cd-fg-cdfg
b) abef+bcd/1-cd-fg-cdfg
c) adcdefg/1-cd-fg-cdfg
d) abcd+efg/1-cd-fg-cdfg

Q4. A.C. servomotor is basically a ____________

a) Three phase induction motor
b) Two phase induction motor
c) Universal motor
d) Single phase induction motor
Q5. The Static system can be defined as:

a) Output of a system depends on the present as well as past input.

b) Output of a system depends only on the received inputs.
c) Output of the system depends on future inputs.
d) Output of the system depends only on the present input.

Q6. Find the function f(t) for the following function F(s):

a)0.25e-t+0.05e-5t
b)-0.2-0.25e-t+0.05e-5t
c)-0.2+0.25e-t+0.05e-5t
d)0.25e-5t+0.05e-t
Q7. The transfer function of a control system is given by G(s) = 25/ (s^2 + 6s + 25). The first maximum
value of the response occurs at t, which is given by:

a)π⁄2
b)π⁄8
c)π⁄4
d)π
Q8. The controller required to handle fast process load changes is:

a) PD controller
b) PI Controller
c)PID Controller
d)None of the above

Q9. The type 1 system has ______ at the origin.

(a)no pole
(b) net pole
(c) simple pole
(d) two poles

Q10. The open-loop transfer function of a unity feedback control system is

The position, velocity, and acceleration error constant are respectively

a)0,0,4K
b) ∞, K/8,0
c)0, 4K, ∞
d) ∞,∞,K/8
Q11. Determine the transfer function of the given system:

a) G1G2G3/ (1 + H2G2G3 + G2G1H1)

b) G1 G2G3/ (1 + G1G2G3H2H1)
c)G1G2G3 / (1 + G1G2G3H1 + G1G2G3H2)
d)G1G2G3 / (1 + G1G2G3H1)

Q12. Find the overall transfer function of the given signal flow graph.

a) G1G2G3/ (1 + G1H1 + G3H2 + G3G1H1H2)

b) G1G3/ (1 + G1H1 + G3H2 + G3G1)
c) (G1G2G3 + G1H1)/ (1 + G1H1 + G3H2 + G3G1H1H2)
d) (G1G2G3 + G1H1 + G3H2) / (1 + G1H1 + G3H2 + G3G1H1H2)
Q13.If the characteristic equation of the closed loop system is s^2 + 2s + 2 = 0, then the system is:

a) Over damped
b) Critically damped
c) Undamped
d)Underdamped

Q14.The step error coefficient of a system G(s) = 1/ (s+2) (s+3) with unity feedback is:

a)0
b) Infinite
c)1
d)1/6
Q15. A system with transfer function 1/Ts+1, subjected to a step input takes to seconds to reach 50%
of step height. The value of t is :
a)6.9s
b)10s
c)14.4s
d) 20s
Q16.The transfer function of a control system is given by G(s) = 25/ (s^2 + 6s + 25). The first maximum
value of the response occurs at t, which is given by:

a) π⁄2
b) π⁄8
c)π⁄4
d)π

Q17. The transfer function of a system is given as 81/ (s^2 + 16s + 81). Find the undamped natural
frequency, damping ratio, and peak time for a unit step input.

a)9, 0.889, 0.762

b)9, 0.559, 0.762
c)9, 0.889, 0.187
d)9, 0.667, 0.187
Q18. The unit step response of a second order system is = 1-e-5t-5te-5t . Consider the following
statements:
1. The under damped natural frequency is 5 rad/s.
2. The damping ratio is 1.
3. The impulse response is 25te-5t.
Which of the statements given above are correct?
a) Only 1 and 2
b) Only 2 and 3
c) Only 1 and 3
d) 1,2 and 3

Q19. In a RLC series circuit, if the resistance R and inductance L are kept constant but capacitance C
is decreased, then which one of the following statements is/are correct?
1. Time constant of the circuit is changed.
2. Damping ratio decreases.
3. Natural frequency increases.
4. Maximum overshoot is unaffected.
a) 1 and 2
b) 2 only
c) 2 and 3
d) 3 and 4

Q20. As unity feedback system has a forward path transfer function G(s) = K/s(s+8) where K is the
gain of the system. The value of K, for making this system critically damped should be
a) 4
b) 8
c) 16
d) 32

Q21. For the system, C(s)/R(s) = 16/(s2+8s+16). The nature of the response will be
a) Overdamped
b) Underdamped
c) Critically damped
d) None of the mentioned

Q22. The transfer function from D(s) to Y(s) is :

a) 2/3s+7
b) 2/3s+1
c) 6/3s+7
d) 2/3s+6

Q23. The overall transfer function of two blocks in parallel are :

a) Sum of individual gain
b) Product of individual gain
c) Difference of individual gain
d) Division of individual gain

Q24. The closed system has higher ________ than open loop control system, this implies increased
speed of response.
a) Gain
b) Bandwidth
c) Frequency
d) Speed

Q25. First order system is defined as :

a) Number of poles at origin
b) Order of the differential equation
c) Total number of poles of equation
d) Total number of poles and order of equation

Q26. 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

Q27. 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

Q28. The advantage of block diagram representation is that it is possible to evaluate the contribution
of each component to the overall performance of the system.
a) True
b) False

Q29. Transfer function of the system is defined as the ratio of Laplace output to Laplace input
considering initial conditions________
a) 1
b) 2
c) 0
d) infinite

Q30. A signal flow graph is the graphical representation of the relationships between the variables of
set linear algebraic equations.
a) True
b) False