Deck 11: Introduction to Alternating Current and Voltage

Question 1

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

Answer 1

False

Question 2

The voltage leads the current in an inductive circuit.

Answer 2

True

Question 3

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

Answer 3

True

Question 4

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 5

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

Question 6

What is the total inductance if a 50 mH inductor is connected in series with a 15 mH inductor?

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

Question 7

An inductor passes direct current and opposes alternating current.

Question 8

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

Question 9

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

Question 10

If a 50 mH inductor operates at equals ________.

A)
B)
C)
D)

Question 11

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

Question 12

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

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

Question 13

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

Question 14

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

Question 15

If an inductor is placed in an ac circuit, the ac voltage across the inductor leads the ac current 10)
through it.

Question 16

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 17

Inductive reactance decreases as frequency increases.

Question 18

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

Question 19

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

Question 20

In an inductive circuit, the ________ lags the ________.

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

Question 21

An 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 22

What is the inductive reactance of a 0.

A)
B)
C)
D)

Question 23

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 24

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

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

Question 25

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

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

Question 26

What is the time constant for a 50 mH inductor and

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

Question 27

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 28

What is the inductive reactance of an inductor that drops 12 VRMS and carries 50 mARMS?

A)
B)
C)
D)

Question 29

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)

Question 30

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

A)
B)
C)
D)

Question 31

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

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

Question 32

If an inductor carries its resistance?

A)
B)
C)
D)

Question 33

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 34

If two 2. what is the circuitʹs maximum current?

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

Question 35

If a 27 m H inductor has a reactance of the frequency equals ________.

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

Question 36

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

A)1 μA
B)10 mA
C)
D)1 mA

Question 37

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 38

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

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

Question 39

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 40

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 41

If a inductor has a reactance, the frequency equals ________.

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

Question 42

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

A)
B)
C)
D)

Question 43

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 44

The most commonplace use for inductors in electronics:

A)passes AC voltages.
B)blocks DC voltages.
C)passes DC voltages.
D)blocks AC voltages.

Question 45

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 46

If an inductor carries 150 resistance?

A)
B)
C)
D)

Question 47

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 48

What is the reactance of a

A)
B)
C)
D)

Question 49

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

A) .
B)
C)
D)

Question 50

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 51

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 52

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 53

What is the reactance of an inductor that carries 1.

A)
B)
C)
D)

Question 54

Reactive power energy and is measured in:

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

Question 55

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

A)ferrite
B)iron
C)air

Question 56

The time constant of an inductor is:

A)inversely proportional to the resistance in the circuit.
B)the time required for voltage 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 57

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 58

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 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

What is the total inductance in Figure 11-1?

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

Question 61

The ripple voltage as measured at the output of a power supply has increased. 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

It has been determined that the source of audible noise for a radio is du to the power supply voltage. How can an inductor be configured to eliminate this noise?

A)Connect the inductor in parallel with the radio.
B)Connect the inductor in series with the radio power wire.
C)An inductor will not affect the noise.
D)both B and C

Question 63

Stray capacitance for a coil becomes a problem:

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

Question 64

Determination of an inductorʹs value can be had by what method(s)?

A)Apply a signal of a known frequency and voltage, then use Ohmʹs law and the inductive reactance formula.
B)Connect the inductor in series with a known value of resistance, apply a square wave of a known voltage value, then use the time constant formula.
C)Use an inductance meter.
D)any of the above