Deck 12: Capacitors

Question 1

Power dissipated by the resistor in a parallel RL circuit can be increased with the addition of a
capacitor in parallel.

Answer 1

True

Question 2

The overall phase angle of a parallel circuit with a resistance of and an inductive reactance of
25 kΩ would be nearly 90 degrees.

Answer 2

False

Question 3

The impedance of an RL series circuit varies inversely with the frequency.

Answer 3

False

Question 4

A high-pass filter passes high frequencies and blocks low frequencies.

Question 5

A low-pass filter passes high frequencies and blocks other frequencies.

Question 6

If the resistance decreases in an RL filter circuit, the cutoff frequency increases.

Question 7

The impedance of a series RL circuit is found by adding the values of using a phasor
diagram.

Question 8

An ohmmeter can be used to accurately test the impedance of an RL circuit.

Question 9

If the frequency is 60 Hz in Figure 12-1, what is the inductance?

A)26.5 mH
B)265 mH
C)3.77 mH
D)3.77 H

Question 10

If the frequency increases in an RL circuit, the impedance decreases.

Question 11

If the frequency increases in Figure 12-1, the current ________.

A)decreases to zero
B)decreases
C)remains the same
D)increases

Question 12

The source voltage always lags the total current in an RL circuit.

Question 13

Calculate the true power in Figure 12-1.

A)1 W
B)10 W
C)400 mW
D)4 W

Question 14

If the frequency increases in Figure 12-1, the phase angle ________.

A)changes to another quadrant
B)increases
C)decreases
D)remains the same

Question 15

If the frequency increases in Figure 12-1, inductance ________.

A)increases
B)decreases
C)decreases to zero
D)remains the same

Question 16

The impedance of a series RL circuit is found by directly adding the values of

Question 17

The source voltage always leads the total current in an RL circuit.

Question 18

What is the impedance in Figure 12-1?

A)
B)
C)
D)

Question 19

The output at the cutoff frequency of a low pass RL filter is 0 V.

Question 20

If the inductance increases in an RL filter circuit, the cutoff frequency increases.

Question 21

If the frequency increases in Figure 12-1, the phase angle ________ and the impedance ________.

A)decreases, decreases
B)decreases, increases
C)increases, decreases
D)increases, increases

Question 22

What change would decrease the power factor in Figure 12-2?

A)Increase the source voltage.
B)Decrease the value of the resistor.
C)Decrease the source voltage.
D)Increase the value of the resistor.

Question 23

What is the apparent power in Figure 12-1?

A)0.8 VA
B)22.27 VA
C)8.94 VA
D)0.4 VA

Question 24

If the frequency decreases in Figure 12-1, the phase angle ________ and the current ________.

A)increases, increases
B)increases, decreases
C)decreases, decreases
D)decreases, increases

Question 25

If the resistor decreases in Figure 12-2, the total current ________.

A)remains the same
B)decreases
C)increases
D)decreases to zero

Question 26

If the resistance increased to in Figure 12-2, the total impedance is ________.

A)
B)
C)
D)

Question 27

What is the cutoff frequency in Figure 12-1?

A)63 Hz
B)30 Hz
C)25 Hz
D)408 Hz

Question 28

If the frequency decreases in Figure 12-1, the phase angle ________ and the impedance ________.

A)increases, increases
B)decreases, decreases
C)decreases, increases
D)increases, decreases

Question 29

If the operating frequency decreases in Figure 12-1, the phase angle ________.

A)changes to another quadrant
B)remains the same
C)increases
D)decreases

Question 30

If the resistance increases in Figure 12-2, the total current ________.

A)decreases
B)decreases to zero
C)remains the same
D)increases

Question 31

If the frequency increases in Figure 12-1, the phase angle ________ and the current ________.

A)decreases, increases
B)increases, decreases
C)decreases, decreases
D)increases, increases

Question 32

If the source voltage changes to 100 V in Figure 12-1, the true power is ________.

A)16 W
B)40 mW
C)4 W
D)40 W

Question 33

Which statement describes the relationship of in Figure 12-2?

A)They are 180° out of phase.
B)
C)They are in phase.
D)

Question 34

If the frequency is 400 Hz in Figure 12-1, what is the inductance?

A)39.8 mH
B)25.12 H
C)39.8 H
D)25.1 mH

Question 35

What is the phase angle in Figure 12-1?

A)86.3°
B)54.3°
C)71.2°
D)63.4°

Question 36

If the operating frequency decreases in Figure 12-1, the current ________.

A)decreases
B)increases
C)decreases to zero
D)remains the same

Question 37

What change would increase the power factor in Figure 12-2?

A)increasing the value of the resistor
B)decreasing the source voltage
C)decreasing the value of the resistor
D)increasing the source voltage

Question 38

What is the total impedance in Figure 12-2?

A)
B)
C)
D)

Question 39

If the operating frequency decreases in Figure 12-1, the inductance ________.

A)decreases
B)remains the same
C)decreases to zero
D)increases

Question 40

What is the voltage across the inductor in Figure 12-1?

A)4.47 V
B)0.4 V
C)0.894 V
D)44.6 V

Question 41

In a RL circuit, the inductive reactance is:

A)directly proportional to the inductance.
B)increases as the frequency increases.
C)directly proportional to the frequency.
D)all of these.

Question 42

What is VOUT at the cutoff frequency in Figure 12-3?

A)14.4 V
B)12.9 V
C)15.6 V
D)15.1 V

Question 43

If a load is purely inductive and the reactive power is 10 VAR, the apparent power is ________.

A)14.14 VA
B)3.16 VA
C)10 VA
D)1.144 VA

Question 44

In an RL filter circuit, the cutoff frequency is defined as the frequency at which:

A)the output voltage drops to 33% of maximum.
B)the output voltage drops to 70% of maximum.
C)the output voltage is cutoff, with minimum or zero output.
D)the output voltage drops to 66% of maximum.

Question 45

If a low-pass RL filterʹs cutoff frequency is 20 kHz, its bandwidth is ________.

A)40 kHz
B)20 kHz
C)0 Hz
D)unknown

Question 46

What effect will an open inductor have on the circuit in Figure 12-3?

A)The current will drop to zero.
B)The output voltage at the cutoff frequency will decrease.
C)The output voltage at the cutoff frequency will increase.
D)The cutoff frequency will increase.

Question 47

If the true power is 10 W and the reactive power is 10 VAR, the apparent power is ________.

A)5 VAT
B)14.1 VA
C)20 VA
D)100 VA

Question 48

When an ac voltage is supplied to an RL circuit, the acʹs current and amplitude will be:

A)similar in waveform.
B)varying in the same manner.
C)lagging the voltage.
D)all of these.

Question 49

An RL high pass filter takes its output across:

A)the series resistor.
B)the parallel resistor.
C)the parallel inductor.
D)the series inductor.

Question 50

In a series RL circuit, as the phase angle between the applied voltage and the total current increases, this is the same as:

A)power factor increasing.
B)true power decreasing.
C)power factor decreasing.
D)apparent power decreasing.

Question 51

The circuit in Figure 12-3 is known as a ________ filter.

A)band-pass
B)low-pass
C)high-pass
D)notch

Question 52

If some of the turns of the inductor in Figure 12-3 have shorted, how will the circuit change?

A)The output voltage at the cutoff frequency will decrease.
B)The cutoff frequency will increase.
C)The output voltage at the cutoff frequency will increase.
D)The cutoff frequency will decrease.

Question 53

Power in an RL circuit can be measured as:

A)
B)true power (Ptrue).
C)
D)all of these.

Question 54

If the resistive current is 2 A and the inductive current is 2 A in a parallel RL circuit, total current is ________.

A)5.66 A
B)2.83 A
C)4 A
D)2 A

Question 55

What is the cutoff frequency in Figure 12-3?

A)7.96 kHz
B)796 Hz
C)637 kHz
D)637 Hz

Question 56

An RL lag network is similar to a:

A)stop pass filter.
B)low pass filter.
C)band pass filter.
D)high pass filter.

Question 57

What is the phase angle in Figure 12-3, at the cutoff frequency?

A)49.9°
B)51.4°
C)45.0°
D)54.3°

Question 58

If the output is taken across the inductor in Figure 12-3, the circuit is known as a ________.

A)low-pass filter
B)band-pass filter
C)notch filter
D)high-pass filter

Question 59

If a high-pass RL filterʹs cutoff frequency is 55 kHz, its bandwidth is theoretically ________.

A)0 kHz
B)55 kHz
C)110 kHz
D)infinite

Question 60

If in a series RL circuit, the source voltage equals ________.

A)14.1 V
B)10 V
C)28.3 V
D)20 V

Question 61

A measured voltage of 0 V across the resistor in a parallel RL circuit would indicate:

A)an open in the resistor.
B)a blown fuse.
C)an short in the inductor.
D)either A or B.

Question 62

The voltage measured across the inductor in a series RL has dropped significantly from normal. What could possibly be the problem?

A)The resistor has gone up in value.
B)partial shorting of the windings of the inductor
C)The resistor has gone down in value.
D)either A or B

Question 63

Which of the following is typically most important of the three types of power in terms of work being done?

A)reactive
B)inductive
C)apparent
D)true

Question 64

After having troubleshot a series RL circuit, you check the resistance of the inductor and it is around 40 ohms. What conclusion does this bring you to?

A)Since the inductorʹs voltage was nearly zero, you are sure the windings have shorted.
B)Since the inductorʹs voltage was nearly zero, the inductor is probably okay so the resistor must be shorted.
C)Since the inductorʹs voltage was nearly zero, the inductor is probably okay, so the resistor must be open.
D)not enough information

Question 65

It is suspected that a high pass filterʹs cutoff frequency has changed. What pieces of test equipment could be used to check it out?

A)an oscilloscope and a square wave generator
B)voltmeter and a sine wave generator
C)either A or B
D)none of the above