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
Question 62
Capacitor value markings are usually:
A. alphanumeric
B. color dabs
C. standard
D. white print