Solved Anna University Question Paper with Answer - 2 (PART B)

PART B (5 × 13 = 65 Marks)

11. (a) Use resistance and source combinations to determine the current i in the Fig. 1. And the power delivered by the 80-V source.

Or

(b) (i) Find the magnitude of total current (IT) and also find out current and voltage drop across the resistors as shown in the Fig. 2. Assume R1 = 100 Ω, R2 = 20 Ω and V = 50 V.

Solution:

Req =  R1 × R2 / R1 + R2

Req = 100 ×  20 / 120

Req = 16.66 Ω

IT = V/R =  50/ 16.66

IT = 3 Amps

Voltage drops are same in the parallel circuits.

Voltage drop acrors R1 is 50, therefore I1= V/R1

I1= 50/100 =  0.5 Amps

Voltage drop across R1 is 50, Therefore I2 = V/R2

I2 = 50/100 = 2.5 Amps

(ii) Find the voltage across the three resistances shown in the Fig. 3.

Solution:

Resistors are connected in series,

Req = R1 + R2 + R3

Req = 10 + 20 + 30

Req = 60 Ω

Total current IT = 60/60 = 1 Amps

The voltage drop acros VR1 = I + R1

= 1 × 10

VR1 = 10 volts

The voltage drop acros VR2 = I + R2

= 1 × 30

VRI = 30 volts

The voltage drop acros VR3 = I + R3

= 1 × 30

VR3 = 30 volts

12. (a) (i) Specify the procedure to solve any given circuit using thevenin theorem.

Refer Page No: 2.23

 (ii) Find the Thevenin's Equivalent circuit for the network faced by the 1 KW

resistor in Fig. 4.

Refer Page No: 2.26 Example No : 2

12. (b) (i) Specify the procedure to solve any given circuit using Norton theorem.

Refer Page No: 2.34 Section No: 2.4.2

(ii) Find the Norton Equivalent circuit for the network faced by the 1 KW resistor in Fig. 5.

Refer Page No: 2.35 Example No : 1

13. (a) Derive the expressions for a current in a source free RD circuit.

 Refer Page No: 3.16 Section No: 3.12.2

Or

(b) Derive the expressions for a current in a source free RL circuit.velo

Refer Page No: 3.7 Section No: 3.12.1

14. (a) (i) Derive the expressions of the phasor relationship for Inductor.

Refer Page No : 5.1 Section No: 5.2

(ii) Find the current flowing through a circuit with a voltage of 5cos (100t-50°) at a frequency ω = 100 rad/s across a 4 h inductor.

V = 5 cos(100t-50°);

ω = 100 rad/s;

L = 4 H.

I = ?

I = V / XL

XL = ω L = 1.0 × 4

= 400 Ω

i = Imax cos (100 t - 50° - 90°)

i = 0.0125 cos (100 t - 140°) A

Or

(b) Explicate in detail about the three phase balanced circuits.

Refer Page No: 4.3 Section No: 4.4

15. (a) Derive the expression to obtain the frequency of parallel resonance.

Refer Page No : 5.19 Section No: 5.3

Or

(b) Elucidate the not convention procedure to obtain the mutual inductance with relevant circuit diagrams.

Refer Page No: 5.43 Section No: 5.12