This set of Basic Electrical Engineering Problems focuses on “Alternating Current in a Capacitive Circuit”.

1. What is the relation between current and voltage in a capacitor?

a) I=1/C*integral(Vdt)

b) I=CdV/dt

c) I=1/CdV/dt

d) I=Ct

View Answer

Explanation: Current=rate of change of charge=> I=dQ/dt. Q=CV, hence I=CdQ/dt.

2. Calculate the current in the capacitor having 2V supply voltage and 3F capacitance in 2seconds.

a) 2A

b) 5A

c) 6A

d) 3A

View Answer

Explanation: Q is directly proportional to V. The constant of proportionality in this case is C, that is, the capacitance. Hence Q=CV.

Q=3*2=6C.

I=Q/t= 6/2=3A.

3. If 2V is supplied to a 3F capacitor, calculate the chance stored in the capacitor.

a) 1.5C

b) 6C

c) 2C

d) 3C

View Answer

Explanation: Q is directly proportional to V. The constant of proportionality in this case is C, that is, the capacitance. Hence Q=CV.

Q=3*2=6C.

4. Which among the following expressions relate charge, voltage and capacitance of a capacitor?

a) Q=C/V

b) Q=V/C

c) Q=CV

d) C=Q^{2}V

View Answer

Explanation: Q is directly proportional to V. The constant of proportionality in this case is C, that is, the capacitance. Hence Q=CV.

5. What happens to the current flow in a fully charged capacitor?

a) Current flow stops

b) Current flow doubles

c) Current flow becomes half its original value

d) Current flow becomes one-fourth its original value

View Answer

Explanation: When a capacitor is fully charged, it does not store any more charge. There is no change in charge with time. Current is the rate of change of charge, hence it becomes zero, or stops.

6. For high frequencies of alternating current, capacitor acts as?

a) Open circuit

b) Short circuit

c) Amplifier

d) Rectifier

View Answer

Explanation: Capacitive impedance is inversely proportional to frequency. Hence at very high frequencies, the impedance is almost equal to zero, hence it acts as a short circuit and there is no voltage across it.

7. For very low frequencies of alternating current, capacitor acts as?

a) Open circuit

b) Short circuit

c) Amplifier

d) Rectifier

View Answer

Explanation: Capacitive impedance is inversely proportional to frequency. Hence at very low frequencies the impedance is almost infinity and hence acts as an open circuit and no current flows through it.

8. Capacitor preferred when there is high alternating current frequency in the circuits is?

a) Electrolyte capacitor

b) Mica capacitor

c) Air capacitor

d) Glass capacitor

View Answer

Explanation: Mica capacitors are preferred for high frequency circuits because they have low ohmic losses and less reactance.

9. If a 2F capacitor has 1C charge, calculate the voltage across its terminals.

a) 0.5V

b) 2V

c) 1.5V

d) 1V

View Answer

Explanation: Q is directly proportional to V. The constant of proportionality in this case is C, that is, the capacitance. Hence C/Q=V.

V=2/1=1V.

10. What is the voltage across a capacitor at the time of switching, that is, when t=0?

a) Infinity

b) 0V

c) Cannot be determined

d) 1V

View Answer

Explanation: At the time of switching, when t=0, the capacitor acts as a short circuit. The voltage across a short is always equal to zero hence the voltage across the capacitor is equal to zero.

**Sanfoundry Global Education & Learning Series – Basic Electrical Engineering.**

To practice all areas of Basic Electrical Engineering Problems, __here is complete set of 1000+ Multiple Choice Questions and Answers__.