Reg. no:

MAHENDRA COLLEGE OF ENGINEERING, SALEMMODEL EXAM-IISecond Semester

Electronics and Communication Engineering DepartmentEE6201 ¾ CIRCUIT THEORY

Date:08.05.2014 Time: Three Hours Maximum: 100 marks

Answer ALL questions.PART A ¾(10 × 2 =20 marks)

1. A 25 ohms resistance has a voltage v=150sin377t volts. Find the corresponding current and power.

2. State ohms law and mention its limitations.3. State reciprocity theorem. 4. State maximum power transfer theorem.5. Define bandwidth.6. State dot rule for coupled coils. 7. Define transient response. 8. What is two port networks? 9. Give the relation between Vph and VL, Iph and IL for a star circuit.10. What are the advantages of three phase system?

PART B ¾ (16 ×5 =80 marks) 11. (a)(i) State and Explain Kirchhoff’s law with an example (5)

(ii) Obtain the current in each resistor in fig shown below using network reduction technique. (3)

(iii) Find the current through supplied by the two batteries shown in fig below. (8)

[OR]

(b) (i) For the circuit shown below, find the current in each branch by nodal analysis method. (8)

(ii) For the circuit show below, find the current flowing through the 10ohm resistor by using mesh analysis method. (8)

12. (a) (i) find the voltage across the 2Ω resistor in the figure given below by using superposition theorem (8)

(ii) Determine the current through the 5Ω resistor in the circuit shown in figure using thevenin’s theorem. (8)

[OR]

(b). (i) find the value of RL in the circuit shown in figure for which maximum power transfer takes place. Compute the value of maximum power transfer takes place. (8)

(ii) Using star delta conversion to find the resistance between terminals ‘AB’ of the circuit shown below. (8)

13. (a) (i) A current source is applied to a parallel combination of R,L,C where R=10Ω, L=1H, C=1µF. (i) compute the resonant frequency, (ii) find the quality factor, (iii)compute the value of bandwidth (iv) compute the lower and upper frequency points of the bandwidth. (10)

(ii) Define quality factor of coil and derive the expression for it in terms of resonance and bandwidth. (6)

[OR]

(b) In the series circuit shown in fig below the switch is closed on position 1 at t=0 at t=1 millisecond, the switch is moved to position 2. Obtain the equation for the current in both intervals and draw the transient current curve. (16)

14. (a) Derive and discuss the transient response of series RLC circuit for a sinusoidal input. (16)

[OR]

(b) Write short notes on (16) (i) Input impedance and output impedance in terms of Z parameter

(ii) Open and short circuit impedance.

15. (a) discuss about the techniques used to measure the power in three phase system. (16)

[OR]

(b) (i) Two wattmeter are used to measure power in a three phase load. The wattmeter readings are 400w and -35w. Calculate total active power, power factor and reactive power. (8)

(ii) A three phase balanced delta connected load of (4+j8) Ω is connected across a 400v, there phase balanced supply. Determine the phase current and line current. Assume the RYB phase sequence. Also calculate the power drawn by the load. (8)

¾¾¾¾¾¾¾¾¾¾¾¾¾