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Flashcards in Unit 16 Deck (28)
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1

Effective ac voltage or effective ac current is the equivalent value of what?

dc voltage or dc current that would produce the same amount of heat in a resistor

2

How do you calculate the frequency?

The number of times the rotor turns in one second

3

(T/F) The waveform for alternating-current circuits is asymmetrical

False

4

A waveform image is used to display the level and direction of _______ and ________

Current : Voltage

5

In an AC generator, the magnitude of the voltage produced depends on what 3 things?

1) Number of turns of wire 2) Strength of the magnetic field 3) Speed at which the coil rotates

6

What does RMS value stand for?

Root-Mean-Square

7

Less current uses bigger or smaller conductor size?

Smaller

8

How do you get non-symmetrical waveforms?

Combination of AC and DC wave forms

9

In generators that produce large quantities of electricity, why would you use an electromagnet over a permanent magnet?

When using an electromagnet you can alter that magnetic field which therefore allows you to control the output voltage

10

Most electricity in the US has a frequency of _____ Hz

60

11

The value of the ac current or voltage waveform at a moment of time is called what?

Instantaneous value

12

(T/F) The effects of electron movement change based on the direction of current flow

False

13

When two waveforms are in step with each other, they are said to be ____

In-phase

14

(T/F) The primary reason for using alternating current is because it's inexpensive to transmit

True

15

A direct-current waveform displays the direction and _____ of the current or voltage

Magnitude

16

A three-phase generator has each of its windings out-of-phase with each other by ______ degrees

120

17

Phase differences are often expressed in degrees; one full wave from equals ______ degrees

360

18

What is the best way to know which waveform is leading or lagging?

Find out which waveform finished its cycle first

19

When describing the relationship between voltage and current, the reference waveform is always ______

Voltage

20

An alternating-current waveform displays the level and direction of the current and voltage for every instant of time for how many revolutions of the rotar?

One

21

"Phase" is a term that indicates the _____ or ______ relationship between two waveforms.

Time : Degree

22

When a magnetic field moves through a coil of wire, what causes the electrons in the wire to flow in a specific direction?

Lines of force of the magnetic field

23

Electrons flow only when there is motion of the conductors relative to the ______ _____

Magnetic Field

24

In generators that produce large quantities of electricity, which of these is stationary and which of them is not? Conductor Coils and Magnetic Field

The conductor coils are stationary and the magnetic field revolves within the coils

25

The maximum value the ac current or voltage waveform reaches is called what?

Peak Value

26

For a pure sine wave:

Effective value = RMS value

27

What are two ways to express frequency?

Hertz or Cycles per second

28

A nonsinusoidal waveform is created when nonlinear ____ distort the sine wave

Loads