Anna University Chennai 2005 B.E CIRCUIT THEORY

Code: A-08 Subject: CIRCUIT THEORY & DESIGN
Time: three Hours Max. Marks: 100
NOTE: There are 11 ques. in all.
ques. one is compulsory and carries 16 marks. ans to Q. 1. must be written in the space given for it in the ans book supplied and nowhere else.
ans any 3 ques. every from Part I and Part II. every of these ques. carries 14 marks.
Any needed data not explicitly given, may be suitably presumed and said.
Q.1 Choose the accurate or best option in the following: (2x8)

a. The avg. power absorbed by a passive network
(A) is always zero.
(B) is always positive.
(C) is always negative.
(D) may be positive or zero but never negative.
b. Millman's theorem yields
(A) equivalent voltage source.
(B) equivalent voltage or current source.
(C) equivalent resistance.
(D) equivalent impedance.
c. The superposition theorem is applicable to
(A) current only. (B) voltage only.
(C) both current and voltage. (D) current , voltage and power.
d. At t = 0+ with zero initial conditions, which of the subsequent acts as an open circuit ?
(A) inductor (B) capacitor
(C) resistor (D) all of these
e. In a parallel RLC circuit, the quality factor at resonance is provided by
(A) (B)
(C) (D)
f. For a reciprocal network, the 2 - port ABCD parameters are related as follows
(A) AD - BC = -1 (B) AD - BC = 0
(C) AD - BC = 0 (D) AC - BD = 1
g. For the circuit shown in Fig.1g, the current i(t) will be:
(A) 7.5 sin (1000 t) A. (B) - 7.5 sin (1000 t) A.
(C) 7.5 cos (1000 t) A. (D) -7.5 cos (1000 t) A.
h. A system characterized by the function H, is at rest for t < 0; if , then for t > 0 is provided by
(A) (B)
(C) (D)
PART I
ans any 3 ques.. every ques. carries 14 marks.
Q.2 Explain the principle of duality. How do we obtain the dual of a provided network ? Determine the dual network for the network provided in Fig 2

Give values of every component of the dual network. (14)

Q.3 a. State and discuss Thevenin's theorem. elaborate its limitations ? (7)
b. Find the Thevenin's equivalent at the terminals a - b for the circuit shown in Fig.3(b). (7)


Q.4 a. Derive the conditions for maximum power transfer to a load from a generator with voltage and internal impedance . Take the impedances and as respectively. (7)
b. For the circuit shown in Fig.4(b), obtain the maximum power that can be transferred to a load across A - B.


Q.5 a. Determine the value of L in terms of R and C such that the impedances of networks (A) and (B) in Fig 5(a) are equal. Under these conditions what will be the impedance of network (C) in Fig. 5(a). (7)


b. For the network of Fig.5(b), determine the Thevenin voltage and the Thevenin impedance , across the terminals a - b. (7)

Q.6 In the network shown in Fig.6, the switch K is closed at t = 0. The network is unenergized before the switch is closed. Determine current (14)

PART II
ans any 3 ques.. every ques. carries 14 marks.
a. Define the ABCD parameters of a 2 port network, and discuss their significance. What relation holds for ABCD parameters for 2 two-port networks connected in cascade ? (7)
b. Find the ABCD parameters for the circuit shown in Fig.7(b) (7)

Q.8 a. Define the z - parameters of a 2 - port network. (4)
b. Determine the z - parameters of the bridged - T network shown in Fig.8(b). (10)

Q.9 Determine a ladder network to realize the subsequent short - circuit admittance functions:
(14)
Q.10 Show that the transfer function for an nth order low-pass Butterworth filter is

n even
and
(14)
Q.11 Answer any 2 of the subsequent :
a. Determine transfer admittance : for the terminated network N shown
in Fig.11(a) interms of the h-parameters of N.

b. Realize the impedance function in Foster -I and
Foster - II forms
c. The provided lattice of Fig.11(c) uses four capacitors and 2 inductors.
obtain an equivalent lattice using four inductors and 2 capacitors. (7 x 2)

Earning:   Approval pending.