Deck 12: Rl Circuits

Question 1

The impedance of a series RL circuit is found by directly adding the values of X_L and R .

Answer 1

False

Question 2

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

Answer 2

False

Question 3

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

Answer 3

False

Question 4

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 5

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

Question 6

Calculate the true power in Figure 12-1.

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

Question 7

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

Question 8

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

Question 9

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

Question 10

$$\text { Figure } 12 < 1$$

-What is the impedance in Figure 12-1?

A) 1120 $\Omega$
B) 104 $\Omega$
C) 1040 $\Omega$
D) 112 $\Omega$

Question 11

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

Question 12

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

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

Question 13

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

Question 14

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

Question 15

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

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

Question 16

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

Question 17

The overall phase angle of a parallel circuit with a resistance of 20 and an inductive reactance of 25 would be nearly 90 degrees.

Question 18

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

Question 19

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

Question 20

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 21

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

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

Question 22

What is the phase angle in Figure 12-1 ?

A) 86.3°
B) 54.3°
C) 71.2°
D) 63.4°

Question 23

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 24

What is the total impedance in Figure 12-2?

A) 5.71
B) 9.09
C) 1.07
D) 1.86

Question 25

What is the cut off frequency in Figure 12-1?

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

Question 26

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

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

Question 27

What is the apparent power in Figure 12-1?

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

Question 28

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 29

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

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

Question 30

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 31

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 32

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

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

Question 33

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 34

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

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

Question 35

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 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

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 38

$$\text { Figure } 12 < 2$$

-If the resistance increased to 10 $\mathrm { k } \Omega$ in Figure 12-2 , the total impedance is__________

A) 13.2 $k \Omega$
B) 3.30 $\mathrm { k } \Omega$
C) 6.61 $\mathrm { k } \Omega$
D) infinite $\Omega$

Question 39

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

A) They are 180° out of phase.
B) I_L lags I_R.
C) They are in phase.
D) I_L leads I_R.

Question 40

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 41

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 42

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 43

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 44

What is the cutoff frequency in Figure 12-3?

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

Question 45

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 46

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 47

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 48

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

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

Question 49

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 50

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

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

Question 51

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

A)5V
B)14.1V
C)20V
D)100V

Question 52

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 53

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

A)similar in Wave form.
B)varying in the same manner.
C)lagging the Voltage.
D)all of these.

Question 54

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

A)The outputVoltage at the cutoff frequency Will decrease.
B)The cutoff frequency will increase.
C)The outputVoltage at the cutoff frequency Will increase.
D)The cutoff frequency Will decrease.

Question 55

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

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

Question 56

Power in an RL circuit can be measured as:

A) apparent power (P_a) .
B) true power (P_true).
C) reactive power (P_r) .
D) all of these.

Question 57

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 58

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

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

Question 59

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 60

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 61

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

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

Question 62

It is suspected that a high pass filterʹs cutoff frequency has changed.W hat 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

Question 63

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 64

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