Deck 21: Inductive Reactance

Question 1

The amount of current in an ac circuit with only inductive reactance is ______________ the applied voltage divided by X_L.

Answer 1

equal to

Question 2

The general use of ______________ is to provide minimum reactance for relatively low frequencies but more for higher frequencies.

Answer 2

inductance

Question 3

Inductor values ______________ 1 mH are generally not practical for use in electronic circuits.

Answer 3

below

Question 4

With iron-core coils, the hysteresis and eddy-current losses ______________ with frequency.

Question 5

For an inductor, the induced voltage, V_L always ______________ the current by 90°.

Question 6

When ______________ current flows in an inductance, the amount of current is much less than the dc resistance alone would allow.

Question 7

Inductive reactance is measured in ______________.

Question 8

There is no inductive reactance for steady ______________ current.

Question 9

The polarity of an inductor's counter emf is always such that it ______________ a change in current.

Question 10

______________ reactance is equal to two times pi times frequency times inductance.

Question 11

Inductor values ______________ 1 μH are generally not practical for use in electronic circuits.

Question 12

For the most part, inductor values below what value are not practical for use in electronic circuits?

A) 1?H
B) 100?H
C) 100 mH
D) 1 mH

Question 13

With iron-core coils, the hysteresis and eddy-current losses

A) increase with frequency
B) decrease with frequency
C) are negligible
D) are extremely high regardless of the frequency

Question 14

For an inductor, the induced voltage V_L always

A) lags the current I by 90°
B) leads the current I by 90°
C) lags the current I by 180°
D) leads the current I by 180°

Question 15

Frequency is equal to

A) 2p x T
B) 2p/T
C) p/T
D) 1/T

Question 16

When alternating current flows in an inductance,

A) the current is less than the dc resistance alone would allow
B) the current is more than the dc resistance alone would allow
C) the ac current is not affected by dc resistance
D) the ac current is not affected by inductance

Question 17

X_L equals

A) 1/2?fL
B) 2?fL
C) 2?/fL
D) f/2?L

Question 18

What is the inductive reactance for steady direct current?

A) 600 ?
B) 75 ?
C) ? ?
D) 0 ?

Question 19

Which of the following is not an example of how X_L is generally used?

A) Block dc
B) High opposition to high frequency ac
C) Little opposition to dc
D) Low opposition to low frequency ac

Question 20

What results from an inductor's counter emf with a varying current?

A) Transformer action
B) Impedance
C) Resistance
D) Inductive reactance

Question 21

The polarity of a coil's counter emf is always such that

A) it aids a change in current
B) it opposes a change in current
C) it aids a change in voltage
D) it opposes a change in voltage

Question 22

Inductive reactance only applies to

A) direct current
B) sine wave ac
C) square wave ac
D) pulse wave ac

Question 23

How much is the X_L for a coil with negligible resistance that has 62.8 V across it with 0.1 A of current?

A) 62.8 ?
B) 628 ?
C) 6280 ?
D) 62,800 ?

Question 24

The values of X_L in series or in parallel are combined

A) the same way as ohms of resistance
B) the same way as farads of capacitance
C) by using Pythagorean's theorem
D) by algebraic addition

Question 25

The combined parallel inductive reactance branch will be

A) greater than the highest branch reactance
B) greater than the lowest branch reactance
C) less than the lowest branch reactance
D) twice that of either reactance

Question 26

When alternating current flows in an inductance, the amount of current is much less than the dc resistance alone would allow.

Question 27

The inductive reactance is the ohms of opposition that an inductance has for sine-wave current.

Question 28

The amount of inductive reactance equals two pi times the frequency plus the inductance.

Question 29

The higher the frequency of the alternating current, and the greater the inductance, the X_L opposition will be increased.

Question 30

There is inductive reactance for steady direct current.

Question 31

The inductive reactance of a coil is a result of the inductor's counter emf with a varying current.

Question 32

X_L is measured in ohms.

Question 33

The constant factor 2p indicates the circular motion from which a sine wave is derived.

Question 34

Very often X_L can be determined from voltage and current measurements.

Question 35

Although L can be determined when X_L and f are known, its value is determined strictly by its physical construction.

Question 36

Since reactance is an opposition in ohms, the values X_L in series or parallel are combined the same way as ohms of resistance.

Question 37

The combined parallel inductive reactance will be greater than the lowest branch reactance.

Question 38

The amount of current in an ac circuit with only inductive reactance is equal to the applied voltage divided by the inductance.

Question 39

In a series circuit containing two inductors and a voltage source, the current is less in the inductor with the higher inductance.

Question 40

In a parallel circuit with two inductors and voltage source, the voltage is the same across both inductors and is equal to the voltage source.

Question 41

The constant factor 2? indicates the circular motion from which a sine wave is derived.