Deck 9: Capacitors

Question 1

If the plate area of a capacitor decreases, the capacitance decreases.

Answer 1

True

Question 2

If the distance between the plates of a capacitor increases, the capacitance decreases.

Answer 2

True

Question 3

Efficient filtering is directly related to RC time constant.

Answer 3

True

Question 4

A capacitor will fully charge in about five time constants.

Question 5

Capacitance is the ability to store voltage.

Question 6

The voltage rating of a capacitor indicates the voltage it will charge up to.

Question 7

When two capacitors are connected in parallel across a dc source, the smaller capacitor drops the larger voltage.

Question 8

Capacitance is a capacitor's ability to store resistance.

Question 9

What is one time constant of a 4.7 µF capacitor in series with a 22 kΩ resistor?

A)1.03 ms
B)103 ms
C)10.3 ms
D)0.103 ms

Question 10

To find the total capacitance of two capacitors in parallel, you must combine them using a similar procedure as resistors in parallel.

Question 11

A capacitor blocks dc and passes ac.

Question 12

When two capacitors are connected in series across a dc source, the smallest capacitor drops the largest voltage.

Question 13

A capacitor can fully charge in one time constant.

Question 14

What is the capacitance of a capacitor that drops 50 V and stores 0.500 µC of charge?

A)0.01 µF
B)0.001 µF
C)1 µF
D)0.1 µF

Question 15

Leakage through a capacitor is undesirable.

Question 16

If a 0.022 µF, 0.022 µF and 0.05 µF capacitor are connected in series across a 25 V source, the voltage drop across the largest capacitor equals .

A)10.2 V
B)4.51 V
C)17.5 V
D)11.8 V

Question 17

If a 0.05 µF and 0.1 µF capacitor are connected in parallel across a 20 V source, the total capacitance equals _ and each capacitor drops _ .

A)0.05 µF, 15 V
B)0.15 µF, 10 V
C)0.10 µF, 20 V
D)0.15 µF, 20 V

Question 18

If the dc working voltage of a capacitor is 100 V, the dielectric must withstand .

A)220 VPP
B)75 VRMS
C)85 VRMS
D)100 VDC

Question 19

Electrolytic capacitors are ideal for alternating current applications.

Question 20

How much charge is stored in a 0.022 µF capacitor that drops 22 V?

A)0.0484 µC
B)0.484 µC
C)48.4 µC
D)4.84 µC

Question 21

How long will it take a 0.047 µF capacitor to fully charge through a 100 kΩ resistor?

A)0.235 ms
B)23.5 ms
C)2.35 s
D)235 ms

Question 22

If a 4.7 µF capacitor and a 10 kΩ resistor are connected in series across 25 VDC, approximately how much voltage will the resistor drop after charging for just one time constant?

A)15.8 V
B)21.6 V
C)9.20 V
D)23.8 V

Question 23

If a 4.7 µF capacitor operates at 10 kHz, XC equals .

A)294 µΩ
B)339 Ω
C)3.39 Ω
D)infinite Ω

Question 24

If four 0.022 µF capacitors are connected in parallel, CT equals .

A)0.088 µF
B)0.022 µF
C)0.044 µF
D)0.049 µF

Question 25

If a 1 µF capacitor and a 10 kΩ resistor are connected in series across 20 VDC, approximately how much voltage will the capacitor drop after charging for just one time constant?

A)12.6 V
B)11.0 V
C)17 V
D)12.1 V

Question 26

What is the capacitance that stores 1.175 µC of charge and drops 25 V?

A)0.047 µF
B)47 µF
C)4.7 µF
D)0.47 µF

Question 27

At what frequency is a 2000 pF capacitor operating if its reactance is 745 Ω?

A)1.01 kHz
B)10.1 kHz
C)1010 Hz
D)107 kHz

Question 28

If a 0.1 µF, 0.1 µF and 0.05 µF capacitor are connected in series across a 75 V source, the voltage drop across the smallest capacitor equals .

A)37.5 V
B)18.8 V
C)50 V
D)100 V

Question 29

How long will it take to completely charge a 0.047 µF capacitor through a 1 MΩ resistor?

A)0.029 s
B)0.047 s
C)0.235 s
D)0.47 s

Question 30

How much charge is stored in a 0.47 µF capacitor that drops 18 V?

A)8.46 µC
B)846 µC
C)0.846 µC
D)84.6 µC

Question 31

How long will it take a 1 µF capacitor to completely discharge through a 47 kΩ resistor?

A)47 s
B)47 ms
C)235 ms
D)235 s

Question 32

If a 1 µF, 2.2 µF and 0.05 µF capacitor are connected in series, CT is less than _ .

A)0.05 µF
B)2.2 µF
C)0.001 µF
D)1 µF

Question 33

If an uncharged capacitor, a resistor, a switch and a 12 V battery are connected in series, what is the voltage across the capacitor after it is fully charged?

A)6 V
B)-6 V
C)12 V
D)24 V

Question 34

If a 22 µF capacitor is connected to a 15 V 400 Hz source, its current equals .

A)18.1 mA
B)829 mA
C)1.81 A
D)55 mA

Question 35

If a 0.1 µF capacitor and a 2.2 kΩ resistor are connected in series across 30 VDC, how much voltage will the capacitor drop after charging for just one time constant?

A)29.4 V
B)28.5 V
C)19.0 V
D)25.9 V

Question 36

If an uncharged capacitor, a resistor, a switch and a 12 V battery are connected in series, what is the voltage across the capacitor at the instant the switch is closed?

A)6 V
B)0 V
C)24 V
D)12 V

Question 37

A capacitor that transfers an ac signal from one stage to another is called a capacitor.

A)transfer
B)bypass
C)filter
D)coupling

Question 38

If an uncharged capacitor, a resistor, a switch and a 12 V battery are connected in series, at approximately what time will the capacitor reach full charge?

A)5 × R × C
B)R × C
C)12 × R × C
D)The time cannot be predicted.

Question 39

If the frequency applied to a capacitor increases, the capacitive reactance .

A)increases
B)remains the same
C)varies up and down
D)decreases

Question 40

What is the minimum dc working voltage rating for a capacitor that must drop 120 VRMS?

A)84.8 V
B)170 V
C)339 V
D)120 V

Question 41

When capacitors are connected in series, their total capacitance act like:

A)resistance connected in series.
B)resistance connected in series -parallel.
C)resistance connected in parallel.
D)all of these.

Question 42

When capacitors are connected in parallel, their total capacitance act like:

A)resistance connected in parallel.
B)resistance connected in series.
C)resistance connected in series -parallel.
D)all of these.

Question 43

How long will it take for a 22 µF capacitor to completely charge through a 47 kΩ resistor?

A)8.272 s
B)2.068 s
C)1.034 s
D)5.17 s

Question 44

What is one time constant of a 47 µF capacitor in series with a 120 kΩ resistor?

A)54.6 s
B)5.64 s
C)564 ms
D)0.564 ms

Question 45

If a 47 µF capacitor is connected to a 20 V, 400 Hz source, the current is .

A)0.851 A
B)425 A
C)8.51 A
D)2.36 A

Question 46

What is CT in Figure 9 -1?

A)70.1 µF
B)8.78 µF
C)25.2 µF
D)82 µF

Question 47

If a 0.047 µF, 0.047 µF and 0.47 µF capacitor are connected in series across a 25 V source, the total capacitance equals _ and each 0.047 µF capacitor drops .

A)0.022 µF, 11.9 V
B)0.022 µF, 25 V
C)0.564 µF, 11.9 V
D)0.564 µF, 1.2 V

Question 48

How much voltage is dropped across a 150 µF capacitor after 3.33 seconds if it is charged by a 50 V source through a 22 KΩ resistor?

A)49 V
B)43.3 V
C)31.8 V
D)47.5 V

Question 49

Reactive power (Pr)in a capacitor is defined as the rate at which a capacitor stores or returns energy and is measured in:

A)volt -ampere reactive.
B)current per time constant.
C)watts reactive.
D)volts per time constant.

Question 50

Electrolytic capacitors differ from many other capacitors in construction in that they are:

A)polarized.
B)larger.
C)sensitized.
D)smaller.

Question 51

How long will it take for a 22 µF capacitor to completely discharge through a 4.7 kΩ resistor?

A)0.827 s
B)0.207 s
C)0.517 s
D)0.103 s

Question 52

There is often a capacitor connected to ground between the bridge rectifier and the voltage regulator in a power supply. In order to limit surge current a bridge and the regulator.
Is inserted between the

A)series capacitor
B)surge capacitor
C)surge resistor
D)a shunt inductor

Question 53

At what frequency is a 0.001 µF capacitor operating if its reactance is 45 kΩ?

A)354 kHz
B)3.54 MHz
C)3.54 kHz
D)35.4 kHz

Question 54

When connecting a large electrolytic capacitor to a circuit with a 100 VDC source, place the negative end of the capacitor .

A)towards the positive side of the source
B)in either position; the polarity is not important
C)towards the negative side of the source

Question 55

The time constant of a capacitor is:

A)directly proportional to the capacitance in the circuit.
B)directly proportional to the resistance in the circuit.
C)the time required to charge to 63% or discharge to 37%.
D)all of these.

Question 56

The time constant for a capacitor for each time period is:

A)a constant factor.
B)37% of the decrease in value.
C)63% of the increase in value.
D)all of these.

Question 57

In a transistor amplifier the input ac signal and the output of the amplifier must be connected in a way that not does affect the dc bias voltage. This is accomplished by using a(n)capacitor.

A)isolation
B)large value
C)small value
D)coupling

Question 58

If a 22 µF and 100 µF capacitor are connected in parallel across a 15 V source, the total capacitance equals _ and the 22 µF capacitor drops .

A)18 µF, 15 V
B)122 µF, 15 V
C)1220 µF, 30 V
D)18 µF, 5.2 V

Question 59

Electrolytic capacitors must be connected into a circuit such that:

A)reversal of polarity does not happen.
B)voltage rating marked is not exceeded.
C)positive lead to positive voltage; negative lead to negative voltage.
D)all of these.

Question 60

If a 0.047 µF capacitor operates at 220 kHz, XC equals .

A)1.54 kΩ
B)154 Ω
C)15.4 kΩ
D)15.4 Ω

Question 61

A 65 Vrms signal is applied to a 10 F capacitor. What is the total peak current?

A)6.5 A
B)153 mA
C)6.5 kA
D)not enough information

Question 62

A commonplace use for capacitors in electronics is to:

A)pass DC voltages only.
B)block DC voltages.
C)block AC voltages.
D)pass both AC and DC voltages.

Question 63

A test instrument designed to be used for the testing of capacitors is the .

A)oscilloscope
B)digital multimeter
C)analog multimeter
D)LCR Meter

Question 64

The removal of high frequency transient voltages with a capacitor is called:

A)coupling.
B)decoupling.
C)bypassing.
D)ac blocking.

Question 65

In a capacitive AC circuit, the phase relationship between the voltage and the current is such that the:

A)current is 180 degrees out of phase with voltage.
B)voltage is 360 degrees out of phase with current.
C)current is leading the voltage.
D)voltage is leading the current.

Question 66

Upon checking the voltage output of a power supply with an oscilloscope, you notice an unusually large amount of ripple. What could possibly be the problem?

A)shorted filter capacitor
B)open filter capacitor
C)shorted load
D)either B or C

Question 67

With three capacitors in series, the current lags the voltage by:

A)30 degrees.
B)45 degrees.
C)90 degrees.
D)none of the above.

Question 68

A common use for electrolytic capacitors found in power supplies is .

A)filtering
B)passing AC
C)decoupling
D)blocking DC

Question 69

What is the small amount of power lost in a capacitive circuit due to the internal resistance of the capacitors?

A)instantaneous power
B)true power
C)reactive power
D)ideal power