# Electric Circuits Questions and Answers – Inductor and Capacitor

This set of Electric Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Inductor and Capacitor”.

1. The symbol used for inductance is __________
a)

b)

c)

d)

Explanation: is the symbol used to represent inductance.

2. The symbol used for capacitance is _____________
a)

b)

c)

d)

Explanation: is the symbol used to represent capacitance.

3. The formula used to find the capacitance C is __________
a) Q/v
b) Qv
c) Q-v
d) Q + v

Explanation: Q=cv. Q-charge, V-voltage, c-capacitance.

4. The capacitor doesn’t allow sudden changes in ___________
a) Voltage
b) Current
c) Resistance
d) Capacitance

Explanation: Any small change in voltage occurs within zero time across the gives an infinite current which is practically impossible. So, in a fixed capacitor, the voltage cannot change abruptly.
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5. The Inductor doesn’t allow sudden changes in ___________
a) Voltage
b) Current
c) Resistance
d) Inductance

Explanation: Any small change in current occurs within zero time across the gives an infinite voltage which is practically impossible. So, in a fixed inductor, the voltage cannot change abruptly.

6. The expression for energy of an inductor ____________
a) ½ LI
b) L/2I
c) ½ L2I
d) ½ LI2

Explanation: E=∫p dt
=∫ LI*(dI/dt).dt
= L∫I dI
= ½ LI2.

7. The units for inductance is _________ and capacitance is ___________
d) Henry, Coulomb

Explanation: The unit for inductance is ‘Henry’ and capacitance is ‘Faraday’.

8. The voltage applied to a pure capacitor of 50*10-6 F is as shown in figure. Calculate the current for 0-1msec.

a) 5A
b) 1A
c) -5A
d) -1A

Explanation: For 0≤t≤1msec,
V (t) =m*t (y=mx form)
→100= 1*10-3*m →m= 1*105
→ V (t) = 1*105t
Current I (t) = c. d (v (t))/dt = 50*10-6* (d (1*105t)/dt) = 5A.

9. If a capacitor of capacitance 9.2F has a voltage of 22.5V across it. Calculate the energy of the capacitor.
a) 5062.5W
b) 506.25W
c) 50.625W
d) 50625W

Explanation: E= ½ cv2.

10. The voltage applied to the 212mH inductor is given by v(t)= 15e-5tv. Calculate the current.
a) 16.782e-10t
b) 15.75e-5t
c) 11.27e-10t
d) 14.15e-5t

Explanation: Current I(t)= 1/L 0∫t v*dt.

11. A voltage across a capacitor of 0.5F is defined by
V (t) = [0, t<0
2t, 0<t<2s
4e-(t-2), t>2s] Find i (t).
a) -2e-(t-2) A
b) -4e-(t-2) A
c) -20e-(t-2) A
d) -12e-(t-2) A

Explanation: i= C*(dv/dt).

12. If the voltage across a capacitor is constant, then current passing through it is ________
a) 1
b) 0
c) -1
d) Infinity

Explanation: I= c*(dv/dt).

13. An Inductor works as a ___________ circuit for DC supply.
a) Open
b) Short
c) Polar
d) Non-polar

Explanation: Induced voltage across an inductor is zero if the current flowing through it is constant. I.e. Inductor works as a short circuit for DC supply.

14. The insulating medium between the two plates of capacitor is known as __________
a) Electrode
b) Capacitive medium
c) Conducting medium
d) Dielectric

Explanation: The conducting surfaces are called electrodes and the insulating medium is called Dielectric.

15. If the current flowing through an inductor of inductance 0.3Henry is 5.3t2+4.7t. Calculate the power.
a) 0
b) 1
c) 16.854t3+22.41t2+6.62t
d) 15.3t3+27.8t2+19

Explanation: P= L*i*(di/dt).

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