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GCSE Physics > 12) Magnetism & the Motor Effect > Flashcards

12) Magnetism & the Motor Effect Flashcards

1
Q

What does magnetism describe?

A

The ability of magnets to attract and repel other magnets

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2
Q

What poles do magnets have?

A

North pole

South pole

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3
Q

What happens when like poles on a magnet are close together?

A

They repel

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4
Q

What happens when opposite poles on a magnet are close together?

A

They attract

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5
Q

What are the 3 pure metals that can be turned into magnets?

A

Iron
Nickel
Cobalt
(steel is not a pure metal)

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6
Q

What are metals that can be turned into magnets called?

A

Magnetic materials

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7
Q

What are properties of magnetic materials?

A

They don’t always act as magnets
Can be attracted but not repelled
Non-magnetic materials will never be attracted

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8
Q

What type of magnets are always magnetic even when they are not near other magnets?

A

Permanent magnets

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9
Q

What do permanent magnets produce?

A

Their own electric field

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10
Q

When do magnetic materials temporarily become magnets?

A

When close to a permanent magnet

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11
Q

What force is always between an induced magnet and a permanent magnet?

A

An attractive force

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12
Q

What are induced magnets?

A

Magnetic materials that become magnets when they are in a magnetic field

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13
Q

When will magnetic materials stop being a magnet?

A

When moved away from a permanent magnet

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14
Q

What do permanent magnets induce in magnetic materials?

A

Temporary poles

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15
Q

How do temporary poles align with permanent magnets?

A

So that the magnetic material is attracted to the permanent magnet

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16
Q

What pole will be induced to a magnetic material if it is next to the north pole of a permanent magnet?

A

A south pole

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17
Q

What type of magnetism is when a magnetic material temporarily becomes a magnet when it’s close to a permanent magnet?

A

Induced magnetism

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18
Q

What are magnetic forces caused by?

A

Invisible magnetic fields

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19
Q

What is a magnetic field?

A

The area around a magnet where another magnet or magnetic material feels a force

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20
Q

What does the strength of a magnetic field depend on?

A

The distance from the magnet

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21
Q

Where is the magnetic field of a magnet strongest?

A

At the magnet’s poles

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22
Q

What do magnetic compasses contain?

A

Small bar magnets

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23
Q

What do arrows on magnetic field lines show?

A

The direction of a magnetic field

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24
Q

What direction do magnetic field arrows always point?

A

North pole to south pole

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25
Q

What is the strength of a magnetic field at any point indicated by?

A

The density of the field lines at that point

26
Q

Where does a compass needle point to?

A

The direction of the Earth’s magnetic field

27
Q

What provides evidence the core of the Earth is magnetic?

A

The magnetic field around Earth with poles at the North and South

28
Q

What magnetic pole is the Earth’s geographical N-pole?

A

Magnetically south

29
Q

What type of magnet does the Earth’s core behave as?

A

A bar magnet

30
Q

What do compasses that are mounted vertically show? (dipping compass)

A

The Earth’s magnetic field enters the Earth at different angles in different places

31
Q

What colour is north on a bar magnet?

A

Red

32
Q

What colour is south on a bar magnet?

A

Blue

33
Q

What type of field does any electric current produce?

A

A magnetic field

34
Q

What are the magnetic field lines around a single conducting wire?

A

Circles

35
Q

What does the strength of a magnetic field created by an electrical current depend on?

A

Size of current

Distance from wire

36
Q

When gripping a wire with your right hand, what do your thumb and fingers show?

A

Thumb- direction of current

Fingers- direction of magnetic field

37
Q

What is a solenoid?

A

A loop of wire coiled into a cylindrical shape

38
Q

What are the magnetic field lines inside of a solenoid?

A

Parallel closely spaced lines

39
Q

What do the individual magnetic fields from each individual coil of a solenoid add up to create?

A

A strong almost uniform magnetic field around the coil

40
Q

What are the magnetic field lines outside of a solenoid?

A

Like a bar magnet, with a clear north and south pole

41
Q

Where is the magnetic field weaker in a solenoid?

A

Outside

42
Q

How does the strength of the magnetic field change for a straight wire?

A

Strongest closest to the wire

43
Q

How does the strength of the magnetic field change for a solenoid?

A

Inside- stong and uniform

Outside- decreases in strength the further away

44
Q

What changes the magnetic field strength for both solenoids and straight wires?

A

The size of the current

45
Q

What is the unit for magnetic field strength?

A

Magnetic flux density (B)

46
Q

What is magnetic flux density measured in?

A

Tesla (T)

47
Q

What is the equation for magentic force produced?

A

force produced = magnetic flux density x current x length of wire
F = B x I x L

48
Q

What 3 things is the force on a wire in a magnetic field directly proportional to? (dependent on)

A

Strength of magnetic field
Length of wire
Current through wire

49
Q

Why do coils carrying an electrical current in a motor rotate in a magnetic field?

A

The current going up one side of the coil is flowing in the opposite direction to the current coming down the other side

50
Q

What does a split-ring commutator do every half-turn of a coil?

A

Reverse the direction of the current

51
Q

Why do split-ring commutators reverse the direction of the current?`

A

To ensure the current is always moving in the right direction to keep the coil rotating

52
Q

What 3 ways can increase the size of the turning force acting on a coil carrying a current?

A

Magnetic field strength
Current through coil
Number of coils in wire

53
Q

What happens to the direction of a magnetic field as the direction of current changes?

A

The magnetic field direction changes

54
Q

What do stationary magnets do to electromagnets inside coils with a changing current?

A

Repeatedly attract and repel the electromagnet

55
Q

How do electromagnets inside speakers create sound?

A

1) Change in current through coil changes magnetic field direction
2) Changing field direction attracts and repels electromagnet to stationary magnet
3) Speakers vibrate backwards and forwards
4) Sound waves are produced

56
Q

What is converted to sound waves by a speaker?

A

Electrical signal

57
Q

What does Fleming’s left hand rule determine?

A

The direction of force in the Motor Effect

58
Q

What does each finger mean in Fleming’s left hand rule?

A

First finger- direction of magnetic field
Second finger- direction of current
Thumb- direction of force (direction conductor would move)

59
Q

What is the motor effect?

A

A wire carrying a current creates a magnetic field

60
Q

What are electromagnets?

A

Solenoids containing iron cores

61
Q

What does the catapult experiment show?

A

A wire carrying a current in a magnetic field experiences a force

62
Q

What is the process of the catapult experiment?

A

When power supply is on a current flows in free wire causing it to move
Swapping poles of the magnet will reverse free wire’s direction of movement
Swapping wires connecting to power supply reverses direction of current
Reversing direction of current reverses direction free wire moves

GCSE Physics (14 decks)

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