Code: A-08 Subject: CIRCUIT THEORY & DESIGN
Time: 3 Hours Max. Marks: 100
NOTE: There are 9 Questions in all.
· Question 1 is compulsory and
carries 20 marks. Answer to Q. 1. must be written in the space provided for it
in the answer book supplied and nowhere else.
· Out of the remaining EIGHT
Questions answer any FIVE Questions. Each question carries 16 marks.
· Any required data not
explicitly given, may be suitably assumed and stated.
Q.1 Choose
the correct or best alternative in the following: (2x10)
a. The free response of RL and RC
series networks having a time constant 
is of the form:
(A)
(B)
(C) 
(D) 
b. A network function can be completely specified by:
(A)
Real
parts of zeros (B) Poles and zeros
(C) Real parts of poles (D)
Poles, zeros and a scale factor
c. In the complex frequency 
, 
has the units of rad/s
and 
has the units of:
(A) Hz (B) neper/s
(C) rad/s (D) rad
d. The following property relates to LC impedance or admittance functions:
(A)
The poles and zeros are simple and lie on the 
-axis.
(B)
There must be either a zero or a pole at
origin and infinity.
(C) The highest (or lowest) powers of numerator
or denominator differ by
unity.
(D) All of the above.
e. The current
in the network is:
(A) 1A (B) 
(C)
(D) 
f. The equivalent circuit of the capacitor shown
is
(A)
(B)
(C) (D)
g. The value of
for the wave form
shown is
(A) 
(B) 1.11
(C) 1 (D) 
h. The phasor diagram for an ideal inductance having current I through it and voltage V across it is :
(A) (B)
(C) (D)
i. If the impulse response is realisable by delaying it appropriately and is bounded for bounded excitation, then the system is said to be :
(A) causal and stable (B)
causal but not stable
(C) noncausal but stable (D) noncausal, not
stable
j. In any lumped network with elements in b
branches, 
for all t, holds good
according to:
(A) Norton’s theorem. (B) Thevenin’s theorem.
(C) Millman’s theorem. (D) Tellegen’s theorem.
Answer
any FIVE Questions out of EIGHT Questions.
Each
question carries 16 marks.
Q.2 a. Simplify the network, shown in Fig.1, using
source transformations: (8)
b. Using
any method, obtain the voltage
across terminals A and
B in the network, shown in Fig.2: (8)
Q.3 a. For the network shown in Fig.3, the switch is
closed at t = 0. If the current in L and
voltage across C are 0 for t < 0, find
. (8)
b. Use the Thevenin equivalent of the
network shown in Fig.4 to find
the value of R which will receive
maximum power. Find also
this power. (8)
Q.4 a. Express the impedance Z (s)
for the network shown in Fig.5 in the
form: 
. Plot its poles
and zeros. From the pole-zero plot, what
can you infer about the
stability of the system? (8)
b. Switch
K in the circuit shown in Fig.6 is opened at t = 0. Draw the
and 
, t > 0+. (8)
Q.5 a. Given
the ABCD parameters of a two-port, determine its z-parameters. (8)
b. Find
the y-parameters
for the network
shown
in Fig.7. (8)
Q.6 a. Distinguish between Chebyshev
approximation and maximally flat approximation as applicable to low pass
filters. What is the purpose of
magnitude and frequency scaling in low pass filter design? (8)
b. Show that the voltage-ratio
transfer-function of the ladder
network shown in Fig.8 is given
by:
. (8)
Q.7 a. Explain the following:
(i)
Phasor. (ii) Resonance.
(iii) Q (iv) Damping
coefficient. (8)
b. Determine the Thevenin equivalent circuit of
the network shown in Fig.9. (8)
Q.8 a. Test whether:
(i)
the
polynomial 
is Hurwitz; and
(ii)
the
function 
positive
constants. (8)
b. A system
admittance function Y(s) has two zeros at 
and two poles at 
with system constant =
1. Synthesise the admittance in the form
of three parallel branches: 
in series, and 
in series. (8)
Q.9 a. Explain the meaning of “zeros
of transmission”.
Determine the
circuit elements of the constant-
resistance bridged- T circuit,
shown in Fig.10, that provides
the voltage-ratio:
.Assume R=1
. (8)
b. Synthesise a ladder network whose
driving-point impedance function is given by 
(8)