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Reg. No. :

J 3904

Second Semester

42

Electrical and Electronics Engineering

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B.E./B.Tech. DEGREE EXAMINATION, MAY/JUNE 2009.

EE 2151 — CIRCUIT THEORY

M

(Common to Electronics and Instrumentation Engineering & Instrumentation and Control Engineering) (Regulation 2008) Time : Three hours

.

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Answer ALL questions.

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Maximum : 100 marks

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PART A — (10 × 2 = 20 marks) 1.

State Kirchoff ’s circuital laws.

2.

Draw the V-I characteristics of ideal voltage source.

3.

State super position theorem.

4.

Calculate the value of RL, so that maximum power is transferred from battery. (fig. 1)

42

N E

H T

B A

R

1

G

Fig.1.

Define Bandwidth.

6.

Define quality factor of a coil.

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5. 7.

Find the Laplace transform of x (t ) = u (t ) + δ (t ) .

8.

Write the integro-differential equation of R-L-C series circuit with supply voltage, E.

9.

Calculate the power I (t ) = I m sin (wt − 135 ° ) .

10.

What are the advantages of 3-phase system over 1-phase system?

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factor

if

V (t) = Vm sin (wt − 45° )

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and

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PART B — (5 × 16 = 80 marks) (a)

For the circuit of fig. 2, find the current in each branch by Nodal method.

1

11.

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(b)

Fig.2. Or Find the current in each branch of the circuit and the total power consumed by the circuit of Fig. 3. Assume E = 50 sin (wt + 45°)

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.

1

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Fig.3. (a)

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Find the Thevenin’s equivalent circuit at (a, b) (Fig.4)

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12.

H T

B A

R

G

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1

(b)

Fig.4. Or For the circuit shown in Fig. 5, find the current flowing through the 10 Ω resistor. (16)

Fig.5. 2/3

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J 3904

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(a)

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For the parallel circuit shown in Fig. 6. find the Resonance frequency, f .

1

13.

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Fig.6. Or

14.

(a)

(i)

Explain the single tuned and double tuned circuit.

(ii)

Derive the formula for mutual inductance in terms of coefficient of coupling and self inductance.

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(b)

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Or

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.

A sinusoidal voltage of frequency 25 Hz is connected in series with switch and R = 10 Ω and L = 0.1 H. Calculate the transient current i (t).

(a)

Prove that for balanced supply and unbalanced load of 3-phase system, two wattmeters are sufficient to measure power.

(b)

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(b)

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15.

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A series circuit consist of R-C in series with switch and supply voltage E, the capacitor has initial charge E 0 . Find the transient voltage VC (t ) when the switch is closed at t = 0 .

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Or

(i)

Derive the formula for total power consumed in unbalanced Y connected load.

(ii)

Explain a method to determine power factor in 3-phase system.

B A

R

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1

G

3/3

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