Fundamentals of Alternating Current

Question 1

The velocity of a conductor through a magnetic field plays a part in determining the amount of emf produced. What are the other two factors that effect emf?

Answer 1

flux density, length of conductor

Question 2

A conductor moving parallel to lines of magnetic force produced _____ emf

Answer 2

minimum

Question 3

When a graph is made of the values of voltage induced in a conductor traveling in a circular motion through a magnetic field, the resultant waveform is called a _____ wave

Answer 3

sine

Question 4

when one positive alternation and one alternation have been completed, one _____ has been completed

Answer 4

cycle

Question 5

One alternation occurs within _____ degrees of an electrical sine wave

Answer 5

180

Question 6

What is electrical frequency?

Answer 6

number of electrical cycles per second

Question 7

What is the unit of measurement for frequency and what is the symbol for this unit of measurement?

Answer 7

hertz, hz

Question 8

what is the time required for one alternation to be completed known as?

Answer 8

cycle

Question 9

When a 6 pole alternator is turned through 1080 mechanical degrees, the sine waveform would have passed through ____ electrical degrees

Answer 9

3240

Question 10

For a sine waveform to have passed through 1440 electrical degrees when the alternator shaft makes two complete revolutions, the alternator must have _____ poles

Answer 10

4

Question 11

What are the two factors that affect the output frequency of alternators

Answer 11

number of poles, speed

Question 12

If the r/min of an alternator is increased, then the output frequency of the alternator is _____

Answer 12

increased

Question 13

When a 4 pole alternator turns at 1500 r/min, the output frequency is ____ hz

Answer 13

50

Question 14

What is meant by the maximum value of an ac sine wave?

Answer 14

the greatest voltage or current in the sine wave

Question 15

What is the symbol used to represent the maximum voltage?

Answer 15

Emax

Question 16

The value of voltage anywhere in its cycle is known as its _____ value and is represented by the symbol _____

Answer 16

instantaneous, e

Question 17

Describe what is meant by the effective value of a voltage sine waveform

Answer 17

the value of an ac voltage that produced heat in a circuit at the same rate as a dc value

Question 18

What are the two aspects of a sine waveform that phasors are intended to represent?

Answer 18

magnitude, time relationship

Question 19

On a phasor diagram, passage of time is shown in degrees and increases in the _____ _____ direction

Answer 19

counterclockwise

Question 20

How does resistance affect an ac circuit?

Answer 20

opposes current

Question 21

how does inductance affect an ac circuit?

Answer 21

opposes change in current

Question 22

how does capacitance affect an ac circuit?

Answer 22

opposes change in voltage

Question 23

how does inductive reactance affect an ac circuit?

Answer 23

limits amount of current

Question 24

how does capacitive reactance affect an ac circuit?

Answer 24

limits amount of current

Question 25

What is the term used to describe the total opposition to current flow in an ac circuit?

Answer 25

impedance

Question 26

Name the three factors that affect the total opposition to current flow in an ac circuit

Answer 26

resistance, inductive reactance, capacitive reactance