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Magnetism Flashcards

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1
Q

What is magnetism?

A

The ability of magnets to attract and repel other magnets without physical contact

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2
Q

What do magnets produce?

A

Magnetic field

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3
Q

What does a magnetic field make other magnets or magnetic materials experience?

A

A force

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4
Q

Why do opposite poles attract when 2 magnets are close?

A

Magnetic fields overlap

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5
Q

What is created when opposite poles are placed near each other?

A

A uniform field

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6
Q

What is a uniform field?

A

A magnetic field that is the same everywhere between the poles

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7
Q

How do you tell if an object is a magnet?

A

It will attract magnetic materials and repel one pole of another magnet

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8
Q

What causes there to be magnetic forces?

A

Magnets producing magnetic field

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9
Q

What are magnetic forces?

A

Forces between magnets

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10
Q

Where is the magnetic field strongest?

A

Poles

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11
Q

Where are the magnetic forces strongest?

A

Poles

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12
Q

What do permanent magnets always produce?

A

A magnetic field

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13
Q

When a magnetic material is in a magnetic field, what does it become?

A

Induced magnet

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14
Q

What do permanent magnets create in magnetic materials?

A

Temporary poles which align so the magnetic material is attracted to the permanent magnet

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15
Q

Why is the force between a magnet and magnetic material always attractive?

A

Magnetic induction- the South Pole induces a North Pole in the magnetic material and vice versa

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16
Q

What are induced magnets?

A

Magnetic materials that produce a magnetic field in a magnetic field

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17
Q

What happens to an induced magnet when a permanent magnet is taken away?

A

They return to normal and don’t produce a magnetic field

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18
Q

What materials quickly use magnetism?

A

Magnetically soft materials eg iron, nickel and iron alloys

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19
Q

What materials slowly use magnetism?

A

Magnetically hard materials like steel

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20
Q

3 main magnetic elements

A

Iron, nickel, cobalt

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21
Q

What are magnetic materials always attracted to if they are within the magnetic field?

A

A magnetic

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22
Q

Are magnetic materials repelled?

A

No

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23
Q

What is inside a plotting compass?

A

A tiny bar magnet called a needle that lines up with the magnetic field it’s in

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24
Q

Why will the needle of a compass point in the direction of the North Pole when not near a magnet?

A

The earth’s core is magnetic so it generates its own magnetic field

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25
Q

What does an electric current produce?

A

A magnetic field

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26
Q

What will a wire have created around it when a current flows through it?

A

A magnetic field

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27
Q

What will the magnetic field lines created in a wire with a current look like?

A

Concentric circles perpendicular to the wire in the centre

28
Q

What increases the strength of the field in a wire with a current flowing through it?

A

Larger current and closer to the wire

29
Q

What does changing the direction of the current change?

A

The direction of the magnetic field

30
Q

To find the direction of the current what rule is used?

A

Right hand thumb rule

31
Q

What is a solenoid?

A

A loop of wire coiled into a cylindrical shape that carries an electric current

32
Q

What increases the strength of the magnetic field in a solenoid?

A

More loops

33
Q

Where is the magnetic field weak in a solenoid?

A

Outside the solenoid apart from at the ends

34
Q

Where is the magnetic field strong in a solenoid?

A

Inside

35
Q

What increases magnetic field strength in a solenoid?

A

Increasing current, putting an iron block in the centre of the coil

36
Q

Why does an iron core increase magnetic field strength in a solenoid?

A

Becomes an induced magnet when current flows

37
Q

What decreases magnetic field strength of a solenoid?

A

Increased distance from the solenoid

38
Q

The invention of what has increased the use of magnetic materials?

A

Electromagnets

39
Q

What is an electromagnet?

A

A type of magnet in which the magnetic field is produced by an electric current so can be turned on and off

40
Q

3 objects that use electromagnets

A

Fridge doors, maglev trains, MRI machines

41
Q

What is the motor effect?

A

When a current-carrying conductor is put between the poles of 2 magnets so the magnetic fields interact and the magnet and conductor experience a force

42
Q

What causes the motor effect?

A

The magnetic field created by a current interacting with a magnetic field

43
Q

To experience the motor effect what angle must the wire be at to feel the full force?

A

90 degrees to the magnetic field

44
Q

If the wire runs parallel to the magnetic field, what force will it feel?

A

None

45
Q

What does the direction of the force on the wire depend on?

A

The direction of the magnetic field and direction of current flow

46
Q

What rule determines the direction of force of the motor effect?

A

Fleming’s left hand rule

47
Q

What is Fleming’s left hand rule?

A

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

48
Q

What does the size of the force on a conductor in a magnetic field depend on?

A

Magnetic flux density, current size and length of conductor

49
Q

What is the magnetic flux density?

A

Strength of magnetic field

50
Q

What is the force on the wire directly proportional to?

A

The magnetic flux density, the current and the length

51
Q

When the current is at 90 degrees to the magnetic field, what equation can be used to find the force acting on it?

A

Force = magnetic flux density x current x length

52
Q

Why does a solenoid rotate on its axis?

A

Its experiences a force

53
Q

How can the size of the turning force on the solenoid be increased?

A

Increasing current
Increasing magnetic flux density
Increasing number of coils

54
Q

What is electromagnetic induction?

A

The creation of a potential difference and current in a wire experimenting a charge in a magnetic field

55
Q

How can a potential difference be induced?

A

Moving a conductor
Rotating a magnet in a coil of wire
Changing magnetic field through an electrical conductor

56
Q

How is a pd induced in transformers?

A

The magnetic field strength is increased or the charge speed is increased or more turns in a coil of wire

57
Q

What does the induced pd create?

A

A force which acts in the opposite direction to the action that induced it

58
Q

Why does the induced pd create a force which acts in the opposite direction to the action of that induced it?

A

Motor effect

59
Q

What direction does the force induced by the motor effect run?

A

Opposite to the inductive force’s direction

60
Q

What do transformers change?

A

The potential difference in wires carrying alternating currents

61
Q

How do transformers change pd?

A

Induction

62
Q

What are transformers made up of?

A

2 coils- primary and secondary- was hat are joined by an iron core

63
Q

Describe the transformer process

A

Alternating pd/ current applied to primary coil
Alternating current flows through primary coil creating an alternating magnetic field
Alternating magnetic field in iron core due to alternating current
Alternating magnetic field passes through secondary coil due to alternating current
Alternating pd and magnetic field induced in secondary coil

64
Q

How efficient are transformers?

A

100%

65
Q

Why are transformers 100% efficient?

A

All energy transferred to the transformer by the primary coil will be transferred to any component connected to the secondary coil

66
Q

What is equal in each coil?

A

Power

67
Q

Equation for voltage and number of coils in transformers

A

Voltage primary / voltage secondary
=
Number primary coils / number secondary coils

Physics (5 decks)

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