BIEL-028 No. of Printed Pages : 7

DIPLOMA - VIEP - ELECTRONICS AND COMMUNICATION ENGINEERING (DECVI) /

ADVANCED LEVEL CERTIFICATE COURSE IN ELECTRONICS AND COMMUNICATION

ENGINEERING (ACECVI)

Term-End Examination

June, 2017

BIEL-028 : CIRCUITS AND NETWORKS

Time : 2 hours Maximum Marks : 70

Note : Attempt five questions in all. Question no. 1 is

compulsory. All questions carry equal marks.

Symbols used have their usual meaning. Use of

scientific calculator is permitted.

1. Choose the correct answer from the given four

alternatives : 7x2=14

(a) The superposition theorem is not applicable for

(i) voltage calculations

(ii) bilateral elements

(iii) power calculations

(iv) passive elements

BIEL-028 1 P.T.O.

(b) An electric network with six independent

nodes will have

(i) 10 loop equations

(ii) 3 loop equations

(iii) 5 loop equations

(iv) 7 loop equations

(c) Which of the following theorems is used for

linearity test ?

(i) Superposition theorem

(ii) Thevenin's theorem

(iii) Norton's theorem

(iv) None of the above

(d) A series R-L circuit with R = 100 ohm,

L = 50 H is supplied to a d.c. source of

100 V. The time taken for the current to

rise 70% of its steady state value is

(i) 0.3 s

(ii) 0.6 s

(iii) 2.4 s

(iv) 70% of the time required to reach the steady state

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(e) A coil with a certain number of turns has a specified time constant. If the number of turns is doubled, its time constant would

(i) remain unaffected

(ii) become double

(iii) become four fold

(iv) get halved

(0 When a sinusoidal voltage is applied across a series R-L circuit having R = X L, the

phase angle will be

(i) 90°

(ii) 45° lag

(iii) 45° lead

(iv) 90° leading

(g) If a series RLC circuit is excited by a 1

voltage e = E sin wt, where LC < „

(i) Current lags behind the applied voltage

(ii) Current leads the applied voltage

(iii) Current is in phase with the applied voltage

(iv) Voltages across L and C are equal

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10A >5 Q <. ?: 2 0 > 4 2A

2. (a) Find the value of resistance 'R' to have

maximum power transfer in the circuit as

shown in Figure 1. Also obtain the amount

of maximum power.

6Q 6V

2A 15Q 3Q

8V

Figure 1

(b) Use nodal analysis to find the currents in

various resistors of the circuit shown in

Figure 2.

5 Q AAAA VVVV

3 SZ 1

Figure 2

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3. (a) A single-phase sinusoidal a.c. voltage

supply is fed to a series R-C circuit.

Determine

(i) the instantaneous expression of the

current flowing in the circuit,

(ii) the impedance,

(iii) the power factor,

(iv) the power consumed, and

(v) the reactive volt-amperes. 7

(b) A resistance, and an inductance are

connected in series across a voltage

v = 238 sin 314t. The current expression is

found to be 4 sin (314t — 4 ). Find the

values of resistance, inductance and power

factor. 7

4. (a) Derive an expression for the current at any

time after switching a sinusoidal voltage

Vn. sin (wt + a) across a series R-C circuit. 7

BIEL-028 5 P.T.O.

(b) In the network shown in Figure 3, switch S

is closed at t = 0, a steady state current

having previously been attained. Solve for

the current as a function of time.

Figure 3

5. (a) Find the Laplace Transform of unit step, unit ramp and unit impulse function.

(b) In the circuit shown in Figure 4, S is closed at time t = 0. Determine i c(t) and the time constant.

Figure 4

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6. (a) Differentiate between low-pass and

high-pass filters. Give one application for

each category.

(b) A simple high-pass R-C filter having a

cut-off frequency of 5 kHz is connected to a

source of supply of constant voltage of 10 V

and variable frequency. Determine

(i) The capacitance C if R = 2000 S2

(ii) The output voltage and its decibel

level when the supply frequency is

(1) cut-off frequency, (2) zero and

(3) 50 kHz.

7. Write short notes on any two of the

following : 2x7=14

(a) Open-circuit and Short-circuit parameters

of a four-terminal network

(b) Relations between h-parameters and ABCD

parameters

(c) Maximum Power Transfer Theorem

BI EL-028

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