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D3 > Magnetism > Flashcards

Magnetism Flashcards

0
Q

What type of reluctance does a temporary Magnet have

A

Low

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1
Q

What type of reluctance does a permanent magnet have

A

High reluctance

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2
Q

Iron content in a permanent magnet

A

Hard and high

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3
Q

Iron in temporary magnet

A

Soft

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4
Q

Three ways that a magnet can be demagnetized

A

AC current heat and vibration

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5
Q

Three elements which are magnetic

A

Iron nickel cobalt

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6
Q

State the law of magnetic repulsion/attraction

A

Opposites attract likes repel

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7
Q

Five properties of magnetic flux lines

A 
Always form complete loops
Represent tension along their length
Repel eachother
Don't cross
Arrange for max number of lines
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8
Q

The lines of force emerge from what pole of a magnet

A

North

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9
Q

Poles inside a magnet flow from

A

South to north

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10
Q

What is reluctance

A

Resistance to magnetic flux

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11
Q

What is permeability

A

A measure of ability to conduct flux

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12
Q

What is a unit of magnetic flux

A

Weber

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13
Q

High carbon steels reluctance compared to iron

A

Low

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14
Q

Type of iron suitable for temporary magnets

A

Soft

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15
Q

Can magnetic flux travel in a vacuum

A

Yes

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16
Q

What is another name for magnetic lines of force

A

Magnetic flux

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17
Q

The magnetic flux and a circuit is directly proportional to the magnetomotive force and inversely proportional to the

A

Reluctance

18
Q

The ease of which fluxes set up in the cross-section of material is called

A

Permeability

19
Q

Magnetic screens are made up of what type of reluctance

A

Low

20
Q

Why don’t magnetic lines of force collapse in the center of a magnet

A

Because they repel eachother

21
Q

Why are there no magnetic poles in the fields surrounding current caring conductor

A

No points for these lines of force diverge or converge

22
Q

Is the field around the conductor more dance or less dense closer to the conductor

A

More

23
Q

As the current in the conductor is decreased what happens to the magnetic lines of force surrounding the conductor

A

The flex lines collapse inward

24
Q

Parallel conductors caring parents in the same direction attracted to other and parallel conductors caring currents in opposite directions

A

Repel

25
Q

Using the left-hand real for coils the thumb points in the direction of

A

North pole of the coil

26
Q

List for things that affect the strength of electromagnetic coil

A

Spacing
Number of turns
Magnitude of current
Core material type

27
Q

Materials that act in the similar way to iron are referred to as

A

Ferromagnetic

28
Q

What is the most practical way of varying the strength of an electromagnet

A

Changing the magnitude of the current through the coil

29
Q

What device connected in series with an electromagnet is normally used to change the current

A

Rheostat

30
Q

The magnetic flux in a circuit is directly proportional to the

A

Magnetomotive force

31
Q

Opposition of formation of flux lines

A

Reluctance

32
Q

The point at which all domains and magnetic materials have aligned themselves the magnetic field is referred to as

A

Theoretical saturation

33
Q

The amount of reverse magnetizing force required to remove the residual magnetism is called the

A

Coercive force

34
Q

The spreading out a flex lines in an air gap is called

A

Fringing

35
Q

Magnetic cores that are constructed of alternating layers of magnetic material are considered

A

Laminated

36
Q

As a reluctance of a magnetic circuit is increased the flux density of a circuit

A

Decreases

37
Q

The term for the leg of flux density behind magnetizing intensity is

A

Hysteresis

38
Q

Magnetic cores are usually constructed from materials

A

High permeability and low reluctance

39
Q

The amount of energy loss due to constant reversals a magnetic field an AC circuits is referred to as

A

Hysteresis loss in the form of heat

40
Q

Defined the term solenoid

A

Helically wound coil

41
Q

The core of a lifting magnet is made for material with what type of retentivity

A

Low

42
Q

Electromagnet switch

A

Relay

D3 (1 decks)

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