11) A control system in which the control action is somehow dependent on the output is
known as
(a) Closed loop system
(b) Semiclosed loop system
(c) Open system
(d) None of the above
12) Which one of the following open-loop transfer functions has root locus parallel to imaginary axis?
a) K/(s + 1)
b) K(s + 1)(s + 2)2
c) K/(s + 2)2
d) K(s + 2)(s + 1)2
13) A system with gain margin close to unity or a phase margin close to zero is
a) relatively stable
b) oscillatory
c) stable
d) highly stable
14) What is the gain margin a system when the magnitude of the polar plot at phase cross over is ‘a’?
a) 1/a
b) -a
c) zero
d) a
15)How many number of branches the root loci of the question equation
s(s + 2)(s + 3) + K (s + 1) = 0
have?
a) Zero
b) One
c) Two
d) Three
16) Which of the following can be used as a tachogenerator in control system ?
a) Microsyn
b) DC servomotor
c) AC servomotor
d) Magnetic amplifier
17) Which of the following may result in instability problem ?
a) Large error
b) High selectivity
c) High gain
d) Noise
18) The characteristic equation of a control system is given by
s5 + s4 + 2s3 + 2s2 + 4s + 6 =0
What is the number of roots of the equation which lie in the right half of s-plane ?
a) Zero
b) 1
c) 2
d) 3
19) The unit step response of a system is 1 – e-t(1 + t). which is this system ?
a) Unstable
b) Stable
c) Critically stable
d) Oscillatory
20) With negative feedback in a closed loop control system. The system sensitivity to parameter variations:
a) Increases
b) Decreases
c) Becomes zero
d) Becomes infinite