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Flashcards in Unit 18 Deck (32)
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1

What are the three main characteristics of an Eddy current?

Flow erratically ; consume power ; and increase the opposition to current flow

2

Because electrons spin, they have their own what?

Magnetic fields

3

What happens as alternating current within a conductor increases, an expanding electromagnetic field field is created through the conductor and the magnetic flux lines cut through the conductor .

Voltage is induced within the conductor

4

The expanding and collapsing magnetic field from an ac circuit induces a voltage in the conductors that repels the flowing electrons towards the surface of the conductor, what is this called?

Skin effect

5

Induced voltage that opposes the current flow is called what?

Counter-electromotive force or CEMF

6

An ac circuit contains inductive reactance because the voltage and current are what with each ohter?

Not in phase

7

In dc circuits, the only property that affects current and voltage flow is _______

Resistance

8

The total opposition to current flow in an ac circuit includes what and what is it called?

Resistance and reactance ; impedance

9

Windings with soft iron cores produce greater self-inductance than windings with an air core because...

Iron cores provide an easy path for magnetic flux

10

This is the property of an electrical circuit that enables it to store electrical energy by a means of an electromagnetic field and to release this energy at a later time

Inductance

11

A self induced voltage waveform is ____ degrees out of phase with the applied voltage waveform

180

12

Will a longer core produce more or less CEMF?

Less

13

CEMF acts to oppose the change in current flowing in the conductor, this property is called what?

Inductive reactance

14

All that is required to induce voltage is a ______ and an external _____ ______ with relative motion between the two

Conductor ; Magnetic field

15

The movement of electrons caused by an external magnetic field is called what?

Induced current

16

Inductive reactance is measured in what?

Ohms

17

When alternating current increases, the polarity of the CEMF within the conductors _____ the conductor's current.

Opposes

18

In a purely inductive circuit, the applied voltage waveform ____ the current waveform by _____ degrees

Leads ; 90

19

CEFM is ____ proportional to the cross-sectional area of the core and ______ proportional to its lengh

Directly ; inversely

20

Besides conductor resistance, alternating current flow contains an additional element called what that opposes the flow of electrons?

Reactance

21

When a conductor is coiled into adjacent loops (helically wound), it is called what?

A winding

22

Impedance is measured in what and what letter is used as the abbreviation?

Ohms ; Z

23

The waveform of the induced voltage in the conductor is ____ degrees out of phase with the circuit current and _____ degrees out of phase with the applied voltage waveform

90 ; 180

24

What are the three major uses of induction?

Transformers, motors, and generators

25

Conductor resistance is directly proportional to its ________ and inversely proportional to to its ______ ___

Length ; Cross-sectional area

26

When alternating current decreases, the polarity of the induced voltage within the conductor _____ the conductor's current.

Aids

27

The amount of the self-induced voltage created within the winding is directly proportional to what three things?

Current flow, windings, and frequency

28

The voltage induced within the conductor caused by its own expanding and collapsing magnetic field is known as what?

Self-induced voltage

29

(T/F) The induced voltage in a conductor carrying alternating current sometimes opposes the change in current flowing through the conductor.

False

30

The associated potential that is established by induced current is called what?

Induced voltage