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Electrical Fundementals > Magnetism > Flashcards

Magnetism Flashcards

1
Q

Magnetic inclination is the least at the.

A

equator.

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2
Q

Ferromagnetic materials can be magnetized.

A

below a certain temperature.

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3
Q

Glass is an example of a.

A

diamagnetic material.

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4
Q

A solenoid of 10 turns per metre carries a current of 5A. If the current is reduced to 2.5A, how many turns would be required to maintain the same magnetic field?

A

20.

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5
Q

Which of the following materials is easiest to magnetize?

A

Soft iron.

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6
Q

To find which end of an electromagnet is the north pole, use the.

A

Right Hand Clasp Rule.

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7
Q

The earth’s magnetic field is greatest at the.

A

magnetic poles.

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8
Q

The lines of magnetic flux from a magnet will.

A

repel each other.

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9
Q

Of the following which pair of materials would most readily become magnetized?

A

Iron and steel.

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10
Q

The core material used for an electromagnet is soft iron because.

A

it demagnetizes easily.

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11
Q

If the North pole of a magnet is brought nearer to the North pole of another magnet.

A

repulsion between them will be increased.

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12
Q

Where is the magnetic dip least?

A

Equator.

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13
Q

When a number of ferrite pieces are grouped together, they.

A

can be used to store binary code.

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14
Q

Ampere turns is calculated by the number of turns.

A

multiplied by current.

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15
Q

The unit of flux is the.

A

Weber.

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16
Q

Lines of magnetic flux pass from.

A

North to South.

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17
Q

Why is ferrite used in memory circuits?

A

High remanence.

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18
Q

Magnetic lines are flowing parallel. They will.

A

repel each other.

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19
Q

The horizontal component of the earth’s magnetic field is most strongly felt at.

A

equator.

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20
Q

Two parallel lines of magnetic flux in the same polarity.

A

repel each other.

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21
Q

Magnetic fields around two parallel conductors carrying current in the same directions will.

A

attract.

22
Q

Magnetic field on a solenoid is.

A

weakest outside the coil.

23
Q

Which of the following is absolute permeability?

A

µ(micro).

24
Q

The symbol for flux density is.

A

B(capital).

25
Q

A paramagnetic material has a relative permeability of.

A

greater than unity.

26
Q

Through which material will magnetic lines of force pass the most readily?

A

Iron.

27
Q

Permanent magnets have.

A

high reluctance, high coercive force.

28
Q

The term used to denote the strength of a magnetic field is.

A

flux density.

29
Q

A soft iron core is used in an ELECTRO magnet because.

A

it has HIGH permeability and LOW coercivity.

30
Q

A non-magnetic metal.

A

has no permeability.

31
Q

What is the effect of inserting an iron core into a current carrying coil?

A

The flux density of the original magnetic field produced by the coil is increased.

32
Q

Flux density will.

A

increase linearly with magnetic flux.

33
Q

Storage of magnets should be.

A

in pairs with keeper plates.

34
Q

The hysteresis loop for a magnetic material is on a graph with.

A

flux density against magnetising force.

35
Q

A material with a narrow hysteresis loop.

A

will have low retentivity.

36
Q

If a bar magnet is cut in half.

A

two bar magnets are formed.

37
Q

Copper is a.

A

diamagnetic material.

38
Q

The MMF of a coil fed with 2 amps and having 10 turns is.

A

20 ampere turns.

39
Q

An example of a paramagnetic material is.

A

iron.

40
Q

Vibration in a magnet causes.

A

flux to decrease.

41
Q

Permeability of a material can be found by.

A

flux density / MMF.

42
Q

When magnetizing a piece of material, magnetic strength will rise.

A

non-linearly with magnetic force.

43
Q

A material exposed to heat will.

A

be harder to magnetise.

44
Q

If cobalt has a permeability of 4800 it is a.

A

ferromagnetic.

45
Q

A material exposed to heat will

A

be harder to magnetise.

The ‘curie’ temperature is the temperature above which the material cannot be magnetised.

46
Q

If cobalt has a permeability of 4800 it is a

A

ferromagnetic.

Cobalt is a hard ferromagnetic silver-white element. http://en.wikipedia.org/wiki/Cobalt

47
Q

Cobalt has a permeability

A

greater than unity.

NIL. http://en.wikipedia.org/wiki/Cobalt

48
Q

Magnetic flux

A

exist in all space around the magnet.

NIL.

49
Q

The ability of a circuit to produce a magnetic flux under the influence of a MMF

A

permeability.

Aircraft Electrical System. Pallett 3rd Edition appendix one page 196.

50
Q

Magnetic flux saturation takes place when

A

the magnetised medium will accept no further lines of flux.

See a B-H diagram.

51
Q

Cables are shielded to prevent ‘H’ magnetic interference in wires with the following material

A

Copper braiding.

Aircraft Electricity and Electronics, Eismin 5th edition Page 78.

52
Q

Spontaneous magnetism is associated with

A

ferromagnetic materials.

NIL. http://www.geo.umn.edu/orgs/irm/hg2m/hg2m_b/hg2m_b.html.

Electrical Fundementals (19 decks)

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