Electronics and Communication Engineering - Networks Analysis and Synthesis

16. 

A series RC circuit has R = 5 Ω and C = 10 μF. The current in the circuit is 5 sin 20000t. The applied voltage is

A. 252 sin (20000t + 45°)
B. 252 sin (20000t - 45°)
C. 252 sin 20000t
D. 252 sin (20000t - 90°)

Answer: Option B

Explanation:

Z = R2 + XC2 = 50

V = 550 sin(20000 t - 45°)

V = 252 sin(20000 t - 45°)


17. 

A capacitor stores 0.15C at 5 V. Its capacitance is

A. 0.75 F
B. 0.75 μF
C. 0.03 F
D. 0.03 μF

Answer: Option C

Explanation:

Q = CV or 0.15 = C(5) or C = 0.03 F.


18. 

A 0.5 μF capacitor is connected across a 10 V battery. After a long time, the circuit current and voltage across capacitor will be

A. 0.5 A and 0 V
B. 0 A and 10 V
C. 20 A and 5 V
D. 0.05 A and 5 V

Answer: Option B

Explanation:

When the capacitor is fully charged, i = 0 and voltage across capacitor is equal to battery voltage.


19. 

For node 1 in figure, KCL equation is

A.
B.
C.
D. none of the above

Answer: Option C

Explanation:

i(t) is the incoming current. The currents leaving node 1 are


20. 

In the circuit of figure, the switch is closed at t = 0. At t = 0+ the current through C is

A. 4 A
B. 2.5 A
C. 3.1 A
D. 0

Answer: Option A

Explanation:

Capacitor behaves as a short-circuit at t = 0.