Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Final > Chapter 7 Electricity > Flashcards

Chapter 7 Electricity Flashcards

1
Q

The electric motor is a machine that can transform electricity into…

A

Rotary motion to perform useful work

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Faraday used oersted’s principle to …

A

Build the worlds first electric motor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

A turning or twisting force that causes rotation is…

A

Torque

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the four principle parts that make up a D.C. Motor

A

Magnetic field, movable conductor, a commutator, and brushes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

We can make the basic D.C. Motor start by itself by giving it what

A

An armature that contains two or more loops

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the rotating element of a D.C. Motor

A

The armature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

The leads from the armature coils are connected to the raised portions of the commutator segments known as

A

Risers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Brushes are made of

A

Conductive material such as carbon with a good deal of graphite in it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Brushes are made to

A

Wear out faster then the commutator because it is cheaper and easier to replace brushes then service the armature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

The field assembly consists of…

A

Pole pieces and field coils

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Most motor housings consist of what parts

A

Field frame, and two end frames

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

The rotor or armature core is made of laminated soft steel to minimize what

A

Eddy current and hysteresis losses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Lap windings are used for what

A

Low voltage, high current motors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Wave windings are for

A

High voltage low current motors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

The cemf opposes

A

Line voltage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Cemf counter electromotive force tends to regulate what

A

Motor speed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

When a load is put on a motor it slows down which reduces cemf but then increases what

A

Emf electromotive force

18
Q

Power output is a measure of mechanical power and is expressed in…

A

Horsepower ratings

19
Q

When a motor has no load it needs little torque and so speeds up to build up cemf in order to blank the armature current and thus the torque

A

Reduce

20
Q

Series motors are useful where sudden changing loads are put on the motor like

A

Cranes, hoists, subway trains

21
Q

To reverse the direction of rotation of a D.C. Motor you have to reverse either the…

A

Field or the armature current

22
Q

Starters are needed to limit the armature….

A

Current that flows when the motor is turned on

23
Q

Type of controller used to operate a motor driven device that needs to be constantly changed in direction and speed

A

Drum controller

24
Q

The natural rate at which the magnetic field rotates about the stator is called the…

A

Synchronous speed

25
Q

On synchronous motors they use blank windings on their rotor which produce an increase in the magnetic induction between stator and rotor

A

Damper windings

26
Q

The starting torque of a three phase synchronous motor is…

A

Zero

27
Q

How can synchronous motors be made self starting

A

By putting a damper winding over their regular wound rotor

28
Q

Synchronous motors use blank blank to magnetize their rotors

A

Magnetic induction

29
Q

Induction motors use blank blank to magnetize their rotors

A

Electromagnetic induction

30
Q

The squirrel cage is located on the

A

Rotor

31
Q

For the induction motor to work the rotor must slip and turn at a rate slightly blank than that of the blank field

A

Less/rotating

32
Q

The double squirrel cage rotor provides higher ….

A

Starting torque

33
Q

The wound rotor motor differs from other induction motors in that it uses resistance in series with its rotor windings through a

A

Slip ring and brush arrangement

34
Q

The stator and rotor of an induction motor act like windings of a….

A

Transformer

35
Q

Since the induction motor relies on electromagnetic induction, it’s rotor cannot run at the…

A

Synchronous speed

36
Q

What is created when the molecules of an iron bar remain aligned in an external magnetic field after the position of the bar in the field has been changed

A

Hysteresis losses

37
Q

A typical hysteresis motor uses what kind of steel in its rotor

A

Cobalt steel

38
Q

The ac repulsion motor resembles a blank motor and an blank motor

A

D.C., induction

39
Q

The repulsion start induction motor starts just like a standard repulsion motor, but it converts and runs as a blank blank induction motor with a wound rotor

A

Single phase

40
Q

Universal motors are fractional horsepower ac series motors specially designed for use on what kind of power

A

Either D.C. Or ac power

41
Q

The hysteresis synchronous motor develops greater

A

Torque

42
Q

The repulsion start induction motor begins as a repulsion motor but runs as a…

A

Wound rotor motor

Final (12 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions