EEE - Capacitors Quiz (or) MCQ | Questions and Answers

1 .

A capacitor consists of_________

A)

Two conductors

B)

Two insulators

C)

Two dielectrics

D)

Two semiconductors

Correct Answer : Two conductors

Explanation : A capacitor consists of two conductors connected in parallel to each other so that it can store charge in between the plates.

2 .

Capacitance increases with __________

A)

Decrease in plate area

B)

Increase in distance between the plates

C)

Increase in density of the material

D)

Decrease in distance between the plates

Correct Answer : Decrease in distance between the plates

Explanation : Capacitance is inversely proportional to the distance between the two parallel plates. Hence, as the distance between the plate decreases, the capacitance increases.

3 .

Capacitance increases with _______

A)

Decrease in plate area

B)

Increase in plate area

C)

Increase in density of the material

D)

Increase in distance between the plates

Correct Answer : Increase in plate area

Explanation : Capacitance is directly proportional to the plate area. Hence as the plate area increases, the capacitance also increases.

4 .

Capacitor preferred when there is high frequency in the circuits is _______

A)

Air capacitor

B)

Glass capacitor

C)

Mica capacitor

D)

Electrolyte capacitor

Correct Answer : Mica capacitor

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

5 .

A 10

F, 20

F, 22

F, and 100

F capacitor are in parallel. The total capacitance is

A)

2.43 µF

B)

4.83 µF

C)

100 µF

D)

152 µF

Correct Answer : 152 µF

6 .

A capacitor and a resistor are connected in series to a sine wave generator. The frequency is set so that the capacitive reactance is equal to the resistance and, thus, an equal amount of voltage appears across each component. If the frequency is increased

A)

VR = VC

B)

VR > VC

C)

VC > VR

D)

VR and VC = 0

Correct Answer : VR > VC

7 .

What is the capacitance when Q = 60 µC and V = 12 V?

A)

5 µF

B)

12 µF

C)

60 µF

D)

750 µF

Correct Answer : 5 µF

8 .

A capacitor of 0.02 µF is larger than

A)

0.000020 F

B)

200,000 pF

C)

2,000 pF

D)

All of the above

Correct Answer : 2,000 pF

9 .

In Question 6, the capacitor will reach full charge in a time equal to approximately

A)

RC

B)

5 RC

C)

6 RC

D)

None of the above

Correct Answer : 5 RC

10 .

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

A)

I=Ct

B)

I=1/CdV/dt

C)

I=1/C*integral(Vdt)

D)

I=CdV/dt

Correct Answer : I=CdV/dt

Explanation : Current=rate of change of charge
I=dQ/dt. Q=CV. C(capacitance) is constant for a given capacitor so I=CdV/dt.

11 .

A 220 Ω resistor is in series with a 2.2 µF capacitor. The time constant is

A)

2.42 µs

B)

24 µs

C)

48 µs

D)

480 µs

Correct Answer : 480 µs

12 .

A capacitor of 2,000 pF is greater than

A)

0.02 ÂµF

B)

0.002 ÂµF

C)

0.0002 ÂµF

D)

0.0000002 ÂµF

Correct Answer : 0.0002 ÂµF

13 .

A 0.47 µF capacitor is across a 2 kHz sine wave signal source. The capacitive reactance is

A)

0.000169 Ω

B)

1.7 Ω

C)

17 Ω

D)

170 Ω

Correct Answer : 170 Ω

14 .

Four 0.15 µF capacitors are in parallel. The total capacitance is

A)

0.15 µF

B)

0.30 µF

C)

0.6 µF

D)

0.8 µF

Correct Answer : 0.6 µF

15 .

Which of the following capacitors is polarized?

A)

electrolytic

B)

mica

C)

ceramic

D)

plastic-film

Correct Answer : electrolytic

16 .

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

A)

1.5C

B)

2C

C)

3C

D)

6C

Correct Answer : 6C

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.

17 .

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

A)

2A

B)

3A

C)

5A

D)

6A

Correct Answer : 3A

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.

18 .

A 12 kHz voltage is applied to a 0.33 F capacitor, and 200 mA of rms current is measured. What is the value of the voltage?

A)

8 V

B)

80 V

C)

80 mV

D)

800 mv

Correct Answer : 8 V

19 .

A 4.7 M Ω resistor is in series with a 0.015 µF capacitor. The combination is across a 12 V source. How long does it take the capacitor to fully charge?

A)

3.5 s

B)

35 ms

C)

70.5 ms

D)

352 ms

Correct Answer : 352 ms

20 .

Of the following capacitors, which one has the highest dielectric constant?

A)

air

B)

mica

C)

glass

D)

paper

Correct Answer : glass

21 .

A 0.01 ÂµF capacitor equals how many picofarads?

A)

100,000 pF

B)

10,000 pF

C)

1,000 pF

D)

100 pF

Correct Answer : 10,000 pF

22 .

The true power in a capacitor is zero.

A)

True

B)

False

C)

--

D)

--

Correct Answer : True

23 .

Five time constants are required for a capacitor to charge fully or discharge fully.

A)

True

B)

False

C)

--

D)

--

Correct Answer : True

24 .

A capacitor blocks A.C. but passes D.C.

A)

True

B)

False

C)

--

D)

--

Correct Answer : False

25 .

A sine wave voltage is applied across a capacitor. When the frequency of the voltage is decreased, the current

A)

ceases

B)

increases

C)

decreases

D)

remains constant

Correct Answer : decreases

26 .

A 4microF capacitor is charged to 120V, the charge in the capacitor would be?

A)

30C

B)

480C

C)

30microC

D)

480microC

Correct Answer : 480microC

Explanation : 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.

27 .

For high frequencies, capacitor acts as ________

A)

Amplifier

B)

Rectifier

C)

Short circuit

D)

Open circuit

Correct Answer : Short circuit

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.

28 .

For very low frequencies, capacitor acts as ______

A)

Open circuit

B)

Rectifier

C)

Amplifier

D)

Short circuit

Correct Answer : Open circuit

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.

29 .

Two 0.68 µF capacitors are connected in series across a 10 kHz sine wave signal source. The total capacitive reactance is

A)

4.68 Ω

B)

11.70 Ω

C)

23.41 Ω

D)

46.8 Ω

Correct Answer : 46.8 Ω

Explaination :

30 .

A 330 pF capacitor and a 220 pF capacitor are each connected across a 6 V dc source. The voltage across the 330 pF capacitor is

A)

0 V

B)

3 V

C)

4 V

D)

6 V

Correct Answer : 6 V

31 .

When the plate area of a capacitor increases,

A)

the capacitance decreases

B)

the capacitance increases

C)

the capacitance is unaffected

D)

the voltage it can withstand increases.

Correct Answer : the capacitance increases

32 .

When the voltage across a capacitor is tripled, the stored charge

A)

triples

B)

doubles

C)

stays the same

D)

is cut to one-third

Correct Answer : triples

33 .

A 2 µF, a 4 µF, and a 10 µF capacitor are connected in series. The total capacitance is less than

A)

1.5 µF

B)

2 µF

C)

4 µF

D)

10 µF

Correct Answer : 1.5 µF

34 .

The dielectric constant is the ability of a material to establish an electric field.

A)

True

B)

False

C)

--

D)

--

Correct Answer : True

35 .

Energy is stored by a capacitor in a magnetic field.

A)

True

B)

False

C)

--

D)

--

Correct Answer : True

36 .

XC is inversely proportional to frequency and capacitance.

A)

True

B)

False

C)

--

D)

--

Correct Answer : True

37 .

Two series capacitors (one 2 µF, the other of unknown value) are charged from a 24 V source. The 2 µF capacitor is charged to 16 V and the other to 8 V. The value of the unknown capacitor is

A)

1 µF

B)

2 µF

C)

4 µF

D)

8 µF

Correct Answer : 4 µF

38 .

A 0.00022 F capacitor equals how many micro-farads?

A)

22 ÂµF

B)

220 ÂµF

C)

2,200 ÂµF

D)

22,200 ÂµF

Correct Answer : 220 ÂµF