Quiz: Electrical Engineering
Topic: Control system
Each question carries 1 mark.
Negative marking: 1/4 mark
Time: 10 Minute
Q1. The type-2 system has ……………at the origin?
(a) No pole
(b) Net pole
(c) Simple pole
(d) Two poles
Q2. With feedback……………reduces?
(a) nSystem stability
(b) System gain
(c) Both a and b
(d) None of the above
Q3. If the gain margin of a system in decibels is negative, the system is
(b) Marginally stable
(d) Could be stable or unstable or marginally stable
Q4. Consider a network function H(s)= (2(s+3))/((s+2)(s+4)). What is the steady state response due to step input?
Q5. A system with gain margin close to unity or a phase margin close to zero is
(a) relative stable
(d) highly stable
Q6. What is the value of the damping ratio of a second order system when the value of
the resonant peak is unity?
Q7. What are the gain and phase angle of a system having the transfer function
G(s) = (s + 1) at a frequency of 1 rad/s?
(a) 0.41 and 0°
(b) 1.41 and 45°
(c) 1.41 and -45°
(d) 2.41 and 90°
Q8. The response c(t) of a system is described by the differential equation
(d^2 c(t))/(dt^2 ) + 4(dc(t))/dt + 5c(t) = 0
The system response is
(c) critically damped
Q9. System is said to be marginally stable, if
(a) Gain crossover frequency > Phase crossover frequency
(b) Gain crossover frequency = Phase crossover frequency
(c) Gain crossover frequency < Phase crossover frequency
(d) Gain crossover frequency ≠ Phase crossover frequency
Q10. The polar plot of a Transfer function passes through the critical point (-1, 0). The
gain margin is
(a) 0 dB
(b) -1 dB
(c) 1 dB
Sol. Type of system=number of poles at origin.
Sol. With positive feedback, system gain reduces.
Sol. For system to be stable, Gain Margin in dB and Phase Margin in degree must be +ve.
NOTE: For unstable system the signs of gain margin and phase margin are always different or they can both be negative.
Sol. steady state response=lim┬(s→0)〖sC(s)=〗 lim┬(s→0)= s×(2(s+3))/((s+2)(s+4))×1/s=3/4
Sol. System with Unity Gain margin and ‘0’ Phase angle is Oscillatory in nature.