# Capacitors MCQ Questions & Answers

Capacitors MCQs : This section focuses on the "Capacitors". These Multiple Choice Questions (MCQs) should be practiced to improve the Capacitors skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.

Question 1

The capacitance C is charged through a resistor R. The time constant of the charging circuit is given by?

A. C/R
B. 1/RC
C. RC
D. R/C

Question 2

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

Question 3

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

A. 1.5C
B. 6C
C. 2C
D. 3C

Question 4

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

A. 2A
B. 5A
C. 6A
D. 3A

Question 5

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

A. 480C
B. 480microC
C. 30C
D. 30microC

Question 6

For high frequencies, capacitor acts as _________

A. Open circuit
B. Short circuit
C. Amplifier
D. Rectifier

Question 7

For very low frequencies, capacitor acts as ________

A. Open circuit
B. Short circuit
C. Amplifier
D. Rectifier

Question 8

A capacitor consists of_________

A. Two conductors
B. Two semiconductors
C. Two dielectrics
D. Two insulators

Question 9

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

A. Electrolyte capacitor
B. Mica capacitor
C. Air capacitor
D. Glass capacitor

Question 10

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

Question 11

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

Question 12

What is the capacitive reactance if I = 1 amp, V = 2 volts, C = 5 F, and frequency = 10 Hz?

A. 0.2
B. 0.5
C. 0.02
D. 0.003

Question 13

After a capacitor has charged for 1 tc, what percentage of current remains in the resistor?

A. 63.2
B. 36.8
C. 13.5
D. 5

Question 14

What is the dielectric constant for ceramic?

A. between 6 and 8000
B. 5
C. between 5 and 1000
D. 3000

Question 15

What is the power factor if the apparent power of a circuit is 5 W, while the true power is 4 W?

A. 0.0 W
B. 0.8 W
C. 1.0 W
D. 1.25 W

Question 16

What is the value of a capacitor labeled 102?

A. 10,000 pF
B. 1000 pF
C. 1000 F
D. 10,000 F

Question 17

What is the voltage across a capacitor after being charged from a 100 V source for a period of one time constant?

A. 37.8 V
B. 38 V
C. 63 V
D. 101 V

Question 18

If the reactive power of a circuit is 50 mW while the apparent power is 64 mW, then what is the true power of the circuit?

A. 14 mW
B. 36 mW
C. 40 mW
D. 114 mW

Question 19

What is the impedance of an ac RC parallel circuit if the resistance is 12 ohms and the capacitive reactance equals 5 ohms?

A. 0.2 ohms
B. 3.5 ohms
C. 4.6 ohms
D. 13 ohms

Question 20

If a capacitor is placed across a 20 V source, what will be the amount of charge after 5 tc?

A. 5.0 V
B. 12.8 V
C. 13.5 V
D. 20 V

Question 21

What is the value of a capacitor that can store two coulombs of charge when 500 volts is applied across its plates?

A. 4 F
B. 250 F
C. 4,000 F
D. 250 F

Question 22

In a 20 Vac series RC circuit, if 20 V is measured across the resistor and 40 V is measured across the capacitor, the applied voltage is:

A. 45 V
B. 50 V
C. 55 V
D. 60 V

Question 23

An 8 V power source is charging a capacitor. How many volts will be across the capacitor at the second time constant?

A. 1 volt
B. 3 volts
C. 5 volts
D. 7 volts

Question 24

A resistor and an output capacitor form a series circuit with a square wave applied. The circuit is:

A. an integrator
B. a differentiator
C. a multiplier
D. a divider

Question 25

A capacitor and an output resistor form a series circuit with a square wave applied. The circuit is:

A. an integrator
B. a differentiator
C. a multiplier
D. a divider

Question 26

How is ac current related to ac voltage in a purely capacitive circuit?

A. AC current is 0.707 of the ac voltage.
B. AC current lags ac voltage.
C. AC current is 0.637 of the ac voltage.
D. AC current leads ac voltage.

Question 27

A capacitor stores energy within a dielectric between the conducting plates in the form of:

A. a magnetic field
B. positive voltage
C. negative voltage
D. an electric field

Question 28

Which of the following statements is true?

A. The voltage to which a capacitor is charged can change instantaneously.
B. The current in a capacitive circuit takes time to change.
C. A fully charged capacitor appears as a short to dc current.
D. An uncharged capacitor appears as a short to an instantaneous change in current.

Question 29

In an ac circuit, an output capacitor and a resistor are connected in series with an ac signal. What filter action will be the result?

A. bandpass
B. low-pass
C. high-pass
D. band-stop

Question 30

In an ac circuit, a capacitor and an output resistor are connected in series with an ac signal. What filter action will be the result?

A. bandpass
B. low-pass
C. high-pass
D. band-stop

Question 31

If the dielectric constant of a capacitor is decreased, then its capacitance will:

A. increase
B. decrease
C. remain the same
D. be destroyed

Question 32

In a capacitive circuit, current flow is limited to

A. charging periods
B. discharging periods
C. neither charging periods nor discharging periods
D. both charging periods and discharging periods

Question 33

As a capacitor is being charged, current flowing into the capacitor will:

A. increase
B. decrease
C. remain the same
D. cannot tell

Question 34

What is the reactance value for a capacitor installed in a dc circuit?

A. zero
B. moderate
C. infinite
D. cannot tell

Question 35

The strength of an electric field at a given point is proportional to the potential difference on the plates and inversely proportional to the:

A. plate separation
B. negative plate only
C. field strength
D. charge difference

Question 36

In a purely capacitive circuit,

A. current leads voltage by 90°
B. voltage leads current by 90°
C. current lags voltage by 90°
D. current and voltage have a phase relationship of 0°

Question 37

For a given charge difference, electrostatic field strength varies according to:

A. plate differential
B. plate area
C. plate distance
D. dielectric quantity

Question 38

A capacitor is constructed of two parallel:

A. conductors
B. semiconductors
C. inductors
D. dielectrics

Question 39

You could increase the time constant of an RC circuit by

A. adding a resistor in parallel with the circuit resistance
B. adding a capacitor in parallel with the circuit capacitance
C. increasing the amplitude of the input voltage
D. exchanging the position of the resistor and capacitor in the circuit

Question 40

A capacitor's rate of charge is considered:

A. magnetic
B. a current block
C. linear
D. exponential

Question 41

When a circuit consists of a capacitor and a resistor in series with a voltage source, and the voltage across the resistor is zero, then the capacitor is:

A. charging
B. discharging
C. fully charged
D. fully discharged

Question 42

A source voltage across a capacitor will:

A. lead the current by 90 degrees
B. lead the current by 180 degrees
C. lag the current by 90 degrees
D. lag the current by 180 degrees

Question 43

If a charged capacitor is disconnected from a circuit, it will:

A. immediately discharge
B. recharge
C. remain charged
D. leak the charge

Question 44

What do variable capacitors use for dielectric?

A. ceramic, electrolytic, mica, or paper
B. air, ceramic, mica, or plastic
C. ceramic, paper, plastic, or mica
D. mica, ceramic, plastic, or electrolytic

Question 45

If an open capacitor is checked with an ohmmeter, the needle will:

A. stay on zero
B. stay on infinity
C. move from zero to infinity
D. move from infinity to zero

Question 46

Which material has the highest dielectric strength?

A. Air
B. Paper
C. Mica
D. Oil

Question 47

As a capacitor is being charged, the voltage across its terminals will:

A. increase
B. decrease
C. remain the same
D. oppose the source

Question 48

Which of the following determines the capacitance of a capacitor?

A. Plate area, dielectric strength, and plate separation
B. Voltage rating, dielectric constant, and temperature coefficient
C. Temperature coefficient, plate area, and plate separation
D. Plate area, dielectric constant, and plate separation

Question 49

The material used between the plates of a capacitor is called its:

A. insulation material
B. dielectric material
C. separation material
D. plate-divider material

Question 50

What is the total opposition to current in a series RC circuit called?

A. impedance
B. inductance
C. reactance
D. resistance

Question 51

The quantity that represents an ideal capacitor dissipating 0 W of power is

A. instantaneous power
B. true power
C. reactive power
D. resistive power

Question 52

After which time constant can a capacitor be considered to be fully charged?

A. first
B. third
C. fifth
D. seventh

Question 53

A practical capacitor

A. is a short to dc
B. looks like a capacitor in parallel with a resistor
C. is an open to ac
D. stores energy in a magnetic field

Question 54

What is wrong with a leaky capacitor?

A. It is open.
B. It is shorted.
C. The dielectric resistance has increased.
D. The dielectric resistance has decreased.

Question 55

Capacitive reactance values connected in series offer

A. an increase in total XC
B. a decrease in total XC
C. no change in total XC
D. total opposition to voltage in the circuit

Question 56

Power stored from the source and then returned to the source is called:

A. apparent power
B. impedance power
C. reactive power
D. true power

Question 57

Which of the following is the reference vector for parallel RC circuits?

A. R
B. I
C. C
D. V

Question 58

Select the equation below that represents the relationship between charge, capacitance, and voltage for a capacitor.

A. Q = CV
B. C = QV
D. V = IR

Question 59

In an RC circuit, true power (PR) equals:

B. VS × I
C. I2R
D. VT × RT

Question 60

Most older types of paper capacitors have been replaced by which type of construction?

A. electrolytic
B. plastic film
C. oxide casing
D. waxed paper

Question 61

When is a capacitor fully charged?

A. when the voltage across its plates is of the voltage from ground to one of its plates
B. when the current through the capacitor is the same as when the capacitor is discharged
C. when the voltage across the plates is 0.707 of the input voltage
D. when the current through the capacitor is directly proportional to the area of the plates