Capacitors

Q1:
What is the phase shift between the voltage across the resistor and the voltage from the source?

A
VR leads VS by 17°

B
VR leads VS by 73°

C
VR lags VS by 73°

D
VR lags VS by 17°

Q2: What is the total current for a 5 MHz, 1 Vac circuit that consists of a 27 pF capacitor and a 1 k resistor connected in parallel?

A
459 A

B
647 A

C
1.31 mA

D
1.85 mA

Q3: Most older types of paper capacitors have been replaced by which type of construction?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

Q4: 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

Q5: After which time constant can a capacitor be considered to be fully charged?

A first

B third

C fifth

D seventh

Q6:
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

Q7: Which of the following is the reference vector for parallel RC circuits?

A R

B I

C C

D V

Q8: 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

Q9: What is the reactance value for a capacitor installed in a dc circuit?

A zero

B moderate

C infinite

D cannot tell

Q10:
What is the dc charging/discharging time constant for the circuit?

A 294 ps

B 13.5 ms

C 21.25 ms

D 2.16 Gs

Q11: What is the dielectric constant for ceramic?

A between 6 and 8000

B 5.0

C between 5 and 1000

D 3000

Q12: 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 5.0

Q13: As a capacitor is being charged, the voltage across its terminals will:

A increase

B decrease

C remain the same

D oppose the source

Q14: For a given charge difference, electrostatic field strength varies according to:

A plate differential

B plate area

C plate distance

D dielectric quantity

Q15: 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

Q16:
What circuit has the following frequency response?

A bandpass filter

B high-pass filter

C low-pass filter

D integrator

Q17: 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

Q18: 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

Q19: If a charged capacitor is disconnected from a circuit, it will:

A immediately discharge

B recharge

C remain charged

D leak the charge

Q20: If a current of 40 mA flows through a series circuit consisting of a 0.4 F capacitor and a resistor in series with a 4 kHz, 40 Vac source, what is the total circuit impedance?

A
10 omega.gif

B
100 omega.gif

C
1 k omega.gif

D
1 M omega.gif

Q21: 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

Q22: Capacitor value markings are usually:

A alphanumeric

B color dabs

C standard

D white print

Q23: 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

Q24:
What will a 1 F capacitor store?

A one coulomb of charge

B
6.24 x 1012 electrons

C one volt

D
one A of current

Q25:
What is the capacitance of the circuit shown in the given circuit?

A
0.066 mu.gifF

B
0.9 mu.gifF

C
65.97 pF

D
900 pF

Q26: 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

Q27: What is the total opposition to current in a series RC circuit called?

A impedance

B inductance

C reactance

D resistance

Q28: 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

Q29: What is the value of a capacitor labeled 102?

A
10,000 pF

B
1000 pF

C
1000 mu.gifF

D
10,000 mu.gifF

Q30: As a capacitor is being charged, current flowing into the capacitor will:

A increase

B decrease

C remain the same

D cannot tell

Q31: 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

Q32:
What is the reactive power?

A
6.8 mW

B
9.8 mW

C
12.8 mW

D
15.8 mW

Q33:
What is the total capacitance?

A 1 F

B 12 F

C 0.615 F

D 8 F

Q34: 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

Q35: 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

Q36:
What is the impedance of a series RC circuit that consists of a 0.22 F capacitor and a 200-ohm resistor connected to a 3 kHz source?

A 214 ohms

B 313 ohms

C 414 ohms

D 880 ohms

Q37: 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.

Q38: Which material has the highest dielectric strength?

A Air

B Paper

C Mica

D Oil

Q39: A capacitor is constructed of two parallel:

A conductors

B semiconductors

C inductors

D dielectrics

Q40: 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.

Q41: 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

Q42: 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

Q43: If the dielectric constant of a capacitor is decreased, then its capacitance will:

A increase

B decrease

C remain the same

D be destroyed

Q44: 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

Q45:
How long would it take the capacitor in the given circuit to completely discharge if the switch was in position 2?

A 22 ms

B 69 ms

C 345 ms

D 420 ms

Q46:
What is the reactive power in the given circuit?

A 0 VAR

B
691 mu.gifVAR

C
44.23 mVAR

D
1.45 kVAR

Q47: 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

Q48: 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

Q49:
When a 4.7 F capacitor is connected to a 1 kHz source, what is its capacitive reactance?

A 4.7 ohms

B 29.5 ohms

C 34 ohms

D 213 ohms

Q50: 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

Q51: 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

Q52:
What is this circuit?

mcq7_1040_1.gif

A bandpass filter

B high-pass filter

C low-pass filter

D differentiator

Q53: 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

Q54: 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

Q55:
If C1, a 4.7 F capacitor, and C2, a 3.3 F capacitor are in series with 18 Vdc applied, what is the voltage across C1?

A 3.3 V

B 7.4 V

C 6.6 V

D 9.4 V

Q56:
What is the circuit's total current?

A 4.57 mA

B 9.327 mA

C 11.570 mA

D 13.830 mA

Q57:
What is the impedance of this circuit?

A
5928

B
2000

C
1902

D
1798

Q58: 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

Q59: Select the equation below that represents the relationship between charge, capacitance, and voltage for a capacitor.

A Q = CV

B C = QV

C

D V = IR

Q60:
What is the circuit's impedance?

A
1192

B
843

C
723

D
511

Q61:
A capacitor has 25 V across its plates and a stored charge of 1500 mu.gifC. What is the capacitance value?

A
60 pF

B
60 mu.gifF

C
16.67 mF

D
37.5 mF

Q62:
In an RC circuit, true power (PR) equals:

A

B
VS × I

C
I2R

D
VT × RT

Q63: 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

Q64:
What is the voltage across the capacitor?

A 7.07 V

B 1.11 V

C 111 mV

D 7.07 mV

Q65: 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

Q66: 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

Q67: A capacitor's rate of charge is considered:

A magnetic

B a current block

C linear

D exponential

Q68: With a 500 kHz signal source, what would be the value of a capacitor yielding a capacitive reactance of 1 k omega.gif?

A 318 pF

B 2 nF

C 3.18 F

D 2 F

Q69:
How long would it take the capacitor in the given circuit to completely charge if the switch was in position 1?

A 22 ms

B 69 ms

C 345 ms

D 440 ms

Q70: 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

Q71: 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

Q72: What is the angle theta value for a 5.6 F capacitor and a 50-ohm resistor in series with a 1.1 kHz, 5 Vac source?

A 27.3 degrees

B 62.7 degrees

C –27.3 degrees

D –62.7 degrees

Q73: 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°

Q74: 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.


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