Deck 13: Inductors

Question 1

The rate of change of magnetic flux and its proportional induced emf is a form of Lenz's law.

Answer 1

False

Question 2

Figure 13-1
What is the total inductance in the circuit in Figure 13-1?

A) 800 mH
B) 602 mH
C) 2600 µH
D) 2100 mH

Answer 2

2600 µH

Question 3

Any conductor with a current flowing through it is an inductor.

Answer 3

False

Question 4

Inductive reactance opposes a sine wave current, thus reducing the current.

Question 5

A length of wire is wound into a coil to:

A) concentrate the magnetic fields
B) increase the reactance
C) increase the inductance
D) all of the above

Question 6

The inductor always opposes a change in current, even a transient DC current.

Question 7

The time constant of an inductive circuit is dependent on the circuit's resistance.

Question 8

An inductor opposes any change in current through it.

Question 9

Figure 13-1
If the frequency in the circuit in Figure 13-1 is increased to 100 kHz, what is the total inductance?

A) 5200 mH
B) 2600 µH
C) 1600 mH
D) 602 mH

Question 10

Inductance is the property that opposes current flow.

Question 11

Inductive reactance is measured in Henrys.

Question 12

Calculate the induced voltage across a 1 H inductor when the current is changing at a rate of 2 mA per microsecond.

A) 2 V
B) 2000 V
C) 200 V
D) 20 V

Question 13

Voltage leads the current in an inductor.

Question 14

Inductors in parallel increase the total inductance in the circuit.

Question 15

Self-inductance is another term for inductance.

Question 16

Figure 13-1
In addition to pure inductance, what other physical parameters does an inductor contain?

A) reactance
B) capacitance
C) winding resistance
D) both B and C

Question 17

Inductance is measured in Henrys.

Question 18

When a voltage is induced into a conductor or coil) as a result of a change in current through the conductor, the phenomenon is called:

A) self inductance
B) divine inductance
C) parasitic inductance
D) the Henry

Question 19

Energy is stored in an inductor in its electrostatic field.

Question 20

The Unit of inductance is the Henry.

Question 21

Figure 13-3
In the circuit in Figure 13-3, how much time will elapse, after the switch is closed, before the current reaches its maximum value?

A) 1000 µS
B) 1.0 mS
C) 10 µS
D) 100 µS

Question 22

Opposition to current flow without the dissipation of energy in an inductor is called:

A) resistance
B) counter emf
C) inductive reactance
D) impedance

Question 23

Figure 13-3
In the circuit in Figure 13-3, one time constant is equal to:

A) 200 µS
B) 20 µS
C) 0.2 mS
D) 2.0 µS

Question 24

After two time constants on the de-energizing transient, the voltage across the inductor has changed by
%, leaving % remaining.

A) 63.2, 36.8
B) 76.7, 23.3
C) 13.5, 86.5
D) 86.5, 13.5

Question 25

In an inductive circuit, reactance will:

A) depend upon the value of XC
B) be independent from frequency
C) decrease with frequency increase
D) increase with frequency increase

Question 26

The notation di in an inductor refers to:
Dt

A) the rate of change of current with respect to time.
B) the coil permeability as a function of temperature.
C) the ratio of current to number of turns.
D) the magnetizing force applied per turn.

Question 27

If an air core inductor has an inductance of 2 µH, what will the inductance become if an iron core is inserted? Assume that the iron core has a relative permeability µ) of 1000.

A) 2000 µH
B) 63 µH
C) 2nH
D) 2 µH

Question 28

Three parallel inductors of 84 mH, 96 mH, and 160 mH will provide a total inductance of:

A) 113 mH
B) 340 mH
C) 35 mH
D) 205 mH

Question 29

Physical properties that affect inductance are:

A) number of turns, voltage applied, and core material.
B) area of the coil, permeability, and amount of current flow.
C) length of coil, resistance of the coil's wire, and number of turns.
D) core material, number of turns, length of the core, and cross-sectional area of the core.

Question 30

A change of one ampere per second is an inductor that induces a voltage of one volt is considered as which unit value?

A) an Ohm
B) a Lenz
C) a Henry
D) a Farad

Question 31

The formula used to determine total inductance when inductors are connected in parallel is similar to:

A) series capacitors
B) parallel capacitors
C) series inductors
D) series resistors

Question 32

What is the total inductance in the circuit in Figure 13-2?

A) 4.0 H
B) 8.0 H
C) 2.6 H
D) 1.0 H

Question 33

Before an inductor can reach a steady state after a current transient:

A) the circuit must be interrupted.
B) five time constants must have elapsed.
C) the voltage drop across it must remain constant.
D) none of the above.

Question 34

When measured, the voltage drop across an open series-connected inductor:

A) equals the source voltage
B) is minus what is dropped across the meter
C) varies with other components
D) is very low

Question 35

The induced voltage polarity produced by an inductor is explained by:

A) Faraday's law
B) Henry's law
C) Ohm's law
D) Lenz's law.

Question 36

When current flow tries to decrease in an inductor, the magnetic field and the voltage polarity across the inductor _ .

A) collapses, reverses
B) expands, reverses
C) expands, remains the same
D) collapses, remains the same

Question 37

When a DC voltage is first switched across an LR circuit:

A) all the current will flow through the resistor.
B) all the voltage is dropped across the inductor.
C) the maximum current flow is dependent on the inductor.
D) all the voltage is dropped across the resistor.

Question 38

What is the total reactance in Figure ?

A) 3,770 Ω
B) 37.7 Ω
C) 754.0 Ω
D) 377.0 Ω

Question 39

At the instant the switch is closed in Figure 13-3, the inductor acts as:

A) an open circuit
B) a short circuit.
C) a simple resistance
D) a black hole.

Question 40

In an inductor:

A) the voltage leads the current by 45 degrees.
B) the voltage leads the current by 90 degrees.
C) the current leads the voltage by 90 degrees.
D) there is no phase shift between voltage and current.

Question 41

Write the word or phrase that best completes each statement or answers the question.
Complete the following tables. Frequency = 60 Hz
Inductance Reactance 10 H __________

Question 42

Write the word or phrase that best completes each statement or answers the question.
Complete the following tables. Frequency = 60 Hz
Inductance Reactance 10 mH __________

Question 43

Complete the following tables. Frequency = 10 kHz
Inductance Reactance 1000 µH __________

Question 44

Complete the following tables. Frequency = 1.0 kHz
Inductance Reactance 1000 µH __________

Question 45

Write the word or phrase that best completes each statement or answers the question.
Complete the following tables. Frequency = 60 Hz
Inductance Reactance 33 mH __________

Question 46

Complete the following tables. Frequency = 1.0 kHz
Inductance Reactance 0.6 mH __________

Question 47

Complete the following tables. Frequency = 400 Hz
Inductance Reactance 0.33 mH __________

Question 48

Complete the following tables. Frequency = 400 Hz
Inductance Reactance 2 H __________

Question 49

Complete the following tables. Frequency = 1.0 kHz
Inductance Reactance 1000 mH __________

Question 50

Complete the following tables. Frequency = 400 Hz
Inductance Reactance 100 mH __________

Question 51

Complete the following tables. Frequency = 10 kHz
Inductance Reactance 100 mH __________

Question 52

As the resistance of an LR circuit is increased:

A) self-inductance is partially reduced
B) the circuit time constant is increased.
C) induced voltage is greatly increased
D) the circuit time constant is decreased.

Question 53

Complete the following tables. Frequency = 1.0 kHz
Inductance Reactance 200 µH __________

Question 54

A series RL circuit, with R=33K and L=20mH, is driven by a square wave. What is the highest frequency that can be used and still observe the complete waveform?

A) 165KHz
B) 606KHz
C) 16.5KHz
D) 60KHz

Question 55

Write the word or phrase that best completes each statement or answers the question.
Complete the following tables. Frequency = 60 Hz
Inductance Reactance 2 H __________

Question 56

Write the word or phrase that best completes each statement or answers the question.
Complete the following tables. Frequency = 60 Hz
Inductance Reactance 100 mH __________

Question 57

Complete the following tables. Frequency = 400 Hz
Inductance Reactance 1.0 H __________

Question 58

Complete the following tables. Frequency = 10 kHz
Inductance Reactance 25 mH __________

Question 59

Complete the following tables. Frequency = 400 Hz
Inductance Reactance 1000 mH __________

Question 60

Complete the following tables. Frequency = 1.0 kHz
Inductance Reactance 250 mH __________

Question 61

Complete the following tables. Frequency = 1.0 MHz
Inductance Reactance 100 µH __________

Question 62

Complete the following tables. Frequency = 100 kHz
Inductance Reactance 100 µH __________

Question 63

Complete the following tables. Frequency = 10 kHz
Inductance Reactance 1.0 H __________

Question 64

Complete the following tables. Frequency = 100 kHz
Inductance Reactance 1000 µH __________

Question 65

Complete the following tables. Frequency = 1.0 MHz
Inductance Reactance 1 mH __________

Question 66

Complete the following tables. Frequency = 1.0 MHz
Inductance Reactance 10 µH __________

Question 67

Complete the following tables. Frequency = 100 kHz
Inductance Reactance 1 µH __________

Question 68

Complete the following tables. Frequency = 100 kHz
Inductance Reactance 0.1 H __________

Question 69

Complete the following tables. Frequency = 100 kHz
Inductance Reactance 10 µH __________

Question 70

Complete the following tables. Frequency = 1.0 MHz
Inductance Reactance 1 µH __________

Question 71

Complete the following tables. Frequency = 1.0 MHz
Inductance Reactance 10 mH __________

Question 72

Complete the following tables. Frequency = 10 kHz
Inductance Reactance 0.1 H __________