Deck 11: Inductors

Question 1

The total inductance of two parallel inductors equals the sum of their inductance values.

Answer 1

False

Question 2

An iron-core inductor is used in low frequency applications.

Answer 2

True

Question 3

The energy stored in an inductorʹs electromagnetic field is produced by the resistance of the inductorʹs Winding.

Answer 3

False

Question 4

If an inductor is placed in an ac circuit, the ac voltage across the inductor leads the ac current through it.

Question 5

Inductors in series or parallel combine just like resistors in series or parallel.

Question 6

Inductive reactance decreases as frequency increases.

Question 7

An inductor is placed in series With the load for power supply filtration.

Question 8

The voltage leads the current in an inductive circuit.

Question 9

What is the maximum current in a 12 mH inductor if it is connected in series with a 10 resistor and a 15 V_DC source?

A) 6.32 mA
B) 1.5 mA
C) 1.2 mA
D) 2.2 mA

Question 10

Do iron-core inductors or air-core inductors generally have the larger inductance?

A) neither; iron-core inductors and air-core inductors have the same inductance
B) iron core
C) air core
D) There is no way to tell.

Question 11

The voltage and current are in phase in an inductive circuit.

Question 12

True power for an inductor is measured in VAR rather than Watts.

Question 13

If an inductor has an ac current flowing through it, the magnetic field is ________.

A)collapsed
B)steady
C)constantly changing
D)moving from south to north

Question 14

An inductor passes direct current and opposes alternating current.

Question 15

If a 50 mH inductor operates at 22kHz,XL equals_______

A) 113 $\Omega$
B) 1100 $\Omega$
C) 6912 $\Omega$
D) 500 $\Omega$

Question 16

The energy stored in an inductorʹs electromagnetic field is produced by the inductorʹs current.

Question 17

What is the total inductance if a 50 mH inductor is connected in seriesW ith a 15 mH inductor?

A)65 mH
B)50 mH
C)15 mH
D)11.5 mH

Question 18

In an inductive circuit, the ________ lags the ________.

A)voltage, resistance
B)voltage, reactance
C)current,Voltage
D)current, resistance

Question 19

The quality factor for an inductor becomes more apparent at higher frequencies.

Question 20

When a DC voltage is first applied to an inductor, the initial circuit current is zero.

Question 21

If a 50 mH inductor is in series with a 50 resistor across a 50 V_DC source, what is the maximum current that will flow in the circuit?

A) 1
B) 10 mA
C) 100
D) 1 mA

Question 22

If an inductor, resistor and switch are connected in series to a 12 V battery,W hat is the magnitude of the inductorʹs voltage at the instant that the switch is closed?

A)6V
B)4V
C)0V
D)12V

Question 23

What is the inductive reactance of a 0.2 mH inductor operating at 1kHz ?

A) 126
B) 1.26
C) 1.26
D) 126

Question 24

If two inductors are connected in a series AC circuit,Which inductor drops more voltage?

A)It depends upon the frequency.
B)the smaller inductance
C)the larger inductance
D)It depends upon the source Voltage.

Question 25

An 0.05 $\mu \mathrm { H }$ inductance is larger than a_________

A) 0.000000008 H inductance
B) 0.0000005 H inductance
C) 0.000005 H inductance
D) 0.00005 H inductance

Question 26

What is the total inductance of four 10 mH inductors connected in series?

A) 2.5 mH
B) 40,000
C) 40 mH
D) 250 mH

Question 27

What is the inductive reactance of an inductor that drops 12 V_RMS and carries 50 mA_RMS ?

A) 240
B) 600
C) 6
D) 60

Question 28

What is the total inductance of a 14 mH, 22 mH and 45 mH inductor connected in series?

A) 7.2 mH
B) 81 mH
C) 20 mH
D) 81

Question 29

What is the inductive reactance of a 150 mH inductor operating at 10 kHz ?

A) 6280
B) 9420
C) 8450
D) 1500

Question 30

If two 2.5 mH inductors are connected in series with a 4.7 resistor and the source voltage is 100 VDC what is the circuit's maximum current?

A) 7.9 mA
B) 21.3 mA
C) 63.2 mA
D) 1.1 mA

Question 31

What is the time constant for a 50 mH inductor and 5 resistor connected in series?

A) 10 ms
B) 100 s
C) 250 s
D) 10

Question 32

If an inductor carries 100 mADC of current when connected across a 30 VDC source, then what is its resistance?

A) 60
B) 0
C) 300
D) 30

Question 33

What is one time constant for a 10 mH inductor connected in series with a 47 resistor?

A) 0.213
B) 470 mS
C) 213
D) 470 S

Question 34

How many time constants Will it take to completely collapse an inductorʹs magnetic field?

A)3
B)4
C)1
D)5

Question 35

What is the inductance of a 20 mH inductor connected in parallel With a 50 mH inductor?

A)14.3 mH
B)70 mH
C)50 mH
D)20 mH

Question 36

A 0.33 mH inductance is smaller than a ________.

A)0.05 mH inductance
B)33 pH inductance
C)0.0005 H inductance
D)330 pH inductance

Question 37

If a 27 mH inductor has a reactance of 5.5 $k \Omega$ , the frequency equals_____

A) 3.24 kHz
B) 32.4 kHz
C) 932 Hz
D) 324 Hz

Question 38

What is the total inductance of a 40 mH inductor and a 24 mH inductor connected in parallel?

A)15 mH
B)64 mH
C)150 mH
D)32 mH

Question 39

If a 1 mH, 3.3 mH, and 0.1 mH inductor are connected in parallel, L_T equals_______

A) less than 0.1 mH
B) 4.4 mH
C) 5.3 mH
D) greater than 3.3 mH

Question 40

Connecting a ________ inductor in ________With a 100 m H inductor produces a 65 m H inductance.

A)35 mH, parallel
B)186 mH, series
C)35 mH, series
D)186 mH, parallel

Question 41

The quality factor of a coil or inductor is calculated by:

A)
B)
C)
D)

Question 42

When inductors are connected in parallel, their total inductance acts like:

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

Question 43

Which type of inductor core material is likely to produce the least inductance?

A)ferrite
B)iron
C)air

Question 44

If an inductor carries 150 mA_DC of current when connected across a 65 V_DC source, what is its resistance?

A) 26.7
B) 433
C) 30
D) 65

Question 45

What is the reactance of a 100 $\mu \mathrm { H }$ inductor operating at 100 kHz ?

A) 6.28 $\Omega$
B) 62.8 $\Omega$
C) 62.8 $\mathrm { k } \Omega$
D) infinite $\Omega$

Question 46

Connecting a ______inductor in ____with a 70 mH inductor produces a 100 mH inductance.

A) 30 mH , parallel
B) 233 mH , series
C) 233 mH , parallel
D) 30 mH , series

Question 47

How much current flows in the circuit in Figure 11-1 if connected to a 12 VPP, 2 kHz source?

A)4.77 mAp-p
B)10.1 mAp-p
C)60.5 mAp-p
D)126 mAp-p

Question 48

How many time constants Will it take to completely build a magnetic field around an inductor?

A)1
B)2
C)3
D)4
E)5

Question 49

In an inductive AC circuit, the phase relationship between the voltage and the current is such that the:

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

Question 50

What is the reactance of an inductor that carries 1.25 mAP and drops 25 VP at 100 Hz ?

A) 31.3 $\Omega$
B) 3.13 $\mathrm { k } \Omega$
C) 20 $\mathrm { k } \Omega$
D) 15.7 $\mathrm { k } \Omega$

Question 51

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

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

Question 52

What is the total inductance of a 25 mH inductor connected in parallel With a 100 mH inductor?

A)20 mH
B)125 mH
C)less than 20 mH
D)more than 125 mH

Question 53

The most commonplace use for inductors in electronics:

A)passes ACVoltages.
B)blocks DCVoltages.
C)passes DCVoltages.
D)blocks ACVoltages.

Question 54

The time constant of an inductor is:

A)inversely proportional to the resistance in the circuit.
B)the time required forVoltage or current to increase to 63% or to decrease to 37%.
C)directly proportional to the inductance in the circuit.
D)all of these.

Question 55

What is the total inductance in Figure 11-1?

A)95 mH
B)225 mH
C)12.7 mH
D)15.8 mH

Question 56

If a 25 mH inductor drops 50 V while operating at 400 Hz, what is X_L ?

A) 628
B) 62.8
C) 6.28
D) 62.8

Question 57

When inductors are connected in series, their total inductance acts like:

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

Question 58

Inductors ________.

A)have a high resistance to direct current
B)pass direct current
C)block direct current
D)have high reactance to direct current

Question 59

The time constant for an inductor for each time period:

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

Question 60

If a 15 $\mu \mathrm { H }$ inductor has a 2.2 $\mathrm { k } \Omega$
reactance, the frequency equals________

A) 4.28 kHz
B) 23.3 kHz
C) 4.28 MHz
D) 23.3 MHz

Question 61

The ripple voltage as measured at the output of a power supply has increased.W hich of the following could be the problem?

A)partial shorting of the Windings of the filtering coil
B)load resistance has dropped
C)resistance of the coil has decreased
D)either A or B

Question 62

Stray capacitance for a coil becomes a problem:

A)with high frequencies.
B)at resonant frequencies.
C)with ac circuits.
D)with low frequencies.