M.Sc. (Semester II) (CBCS) Examination Nov/Dec-2018
Electronics
CONTROL THEORY
Time: 2½ Hours Max. Marks: 70
Instructions: Attempt five questions.
Q. 1 and 2 are compulsory.
Answer any three questions from Q.3 to Q.7
Figures to the right indicate full marks.
Q.1 Choose the alternatives given below. 08
If roots are on positive real axis of the S plane then the system said to
be
stable unstable
marginally stable none of these
If is open loop transfer function, then closed loop transfer function
is given by


The time that the system output takes to reach from 10 to 90% of its final
value is known as time.
Peak time Settling time
Rise time Delay time
In case of second order system if then the system is
Under damped Critically damped
Undamped Over damped
For tolerance, the settling is given by
Ts wn Ts
Ts wn Ts wn
For polar plots the magnitude is determined by varying gain constant K

From 0 to ∞ From 0 to 1
From 1 to 0 From −∞ to ∞
If poles of the system are s −2 ± 2j then system is
stable unstable
quasi stable none of these
According to Angle condition the phase angle of the functions
is given by
∠G s H s ± 2q 1 1800
∠G s H s ± 2q 1800
∠G s H s 2q 1 900
∠G s H s 2q 3 1800
Page 2 of 2
SLR-VJ-259
State True or false. 06
The graph of log magnitude against frequency is called Bode Plot.
If roots on real positive axis of the s plane then system is unstable.
The transfer function is System is said to be Type
0 system.
If function is having two pole at origin then slope of the Bode plot is
-40dB/decade.
According to Hurwitz's criterion, for sample all Hurwitz determinants
should be positive.
PI controller is an example of discontinuous controller.
Q.2 Answer any two of the following: 10
With suitable examples describes closed loop control system.
Define the term signal flow graph. State properties of signal flow graphs.
Discuss in detail the standard test signals.
Discuss characteristics and application of Proportional control mode. 04
Q.3 What is transfer function of the system? Write a note on Poles and Zeros of
the transfer function of the system. Define order and type of the system.
08
Derive expression for transfer function of the system consisting R and C
connected in series and output is taken across Capacitor.
06
Q.4 Define the terms transient response and steady state response. Discuss
specifications of the transient response.
08
What do you mean by stability of the system? Discuss with respect to S
plane.
06
Q.5 What do you mean by frequency response? Explain with suitable examples. 08
Write a note on Bode Plot. 06
Q.6 What is need of block diagram reduction? Explain in detail the rules used
for block diagram reduction.
08
What is concept of composite control mode? Discuss PID mode in detail. 06
Q.7 What is characteristic equation of second order transfer function? Explain
effect of damping factor on the performance of the second order system.
08
Describe in detail the concept of Polar plots. Draw polar for the function
25/jw