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Basic Electrical Engineering Multiple Choice Questions on “Capacitors”.
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
Answer: B
Clarification: Current=rate of change of charge
I=dQ/dt. Q=CV. C(capacitance) is constant for a given capacitor so I=CdV/dt.
2. If 2V is supplied to a 3F capacitor, calculate the charge stored in the capacitor.
A. 1.5C
B. 6C
C. 2C
D. 3C
Answer: B
Clarification: 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.
3. Calculate the current in the capacitor having 2V supply voltage and 3F capacitance in 2seconds.
A. 2A
B. 5A
C. 6A
D. 3A
Answer: D
Clarification: 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.
4. A 4microF capacitor is charged to 120V, the charge in the capacitor would be?
A. 480C
B. 480microC
C. 30C
D. 30microC
Answer: B
Clarification: Q is directly proportional to V. The constant of proportionality in this case is C, that is, the capacitance. Hence Q=CV.
Q=4*120=480microC.
5. For high frequencies, capacitor acts as _________
A. Open circuit
B. Short circuit
C. Amplifier
D. Rectifier
Answer: B
Clarification: 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.
6. For very low frequencies, capacitor acts as ________
A. Open circuit
B. Short circuit
C. Amplifier
D. Rectifier
Answer: A
Clarification: 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.
7. A capacitor consists of_________
A. Two conductors
B. Two semiconductors
C. Two dielectrics
D. Two insulators
Answer: A
Clarification: A capacitor consists of two conductors connected in parallel to each other so that it can store charge in between the plates.
8. Capacitor preferred when there is high frequency in the circuits is __________
A. Electrolyte capacitor
B. Mica capacitor
C. Air capacitor
D. Glass capacitor
Answer: B
Clarification: Mica capacitors are preferred for high frequency circuits because they have low ohmic losses and less reactance.
9. Capacitance increases with ________
A. Increase in plate area
B. Decrease in plate area
C. Increase in distance between the plates
D. Increase in density of the material
Answer: A
Clarification: Capacitance is directly proportional to the plate area. Hence as the plate area increases, the capacitance also increases.
10. Capacitance increases with __________
A. Increase in distance between the plates
B. Decrease in plate area
C. Decrease in distance between the plates
D. Increase in density of the material
Answer: C
Clarification: Capacitance is inversely proportional to the distance between the two parallel plates. Hence, as the distance between the plate decreases, the capacitance increases.