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Physics GCSE > Electromagnetism > Flashcards

Electromagnetism Flashcards

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1
Q

What happens when electricity is passed through a coil of wire?

A

The coil behaves like a magnet and has a magnetic field around it- this is an electromagnet.

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2
Q

What are the three ways to make an electromagnet stronger?

A
  • wrap the coil of wire around an iron core
  • increase the number of coils
  • increase the size of the current
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3
Q

What is the importance of an electromagnet?

A
  • It can be easily turned on and off

- Therefore electromagnets can be used in scrapyards and as switches in electrical devices.

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4
Q

Investigations to investigate the two other factors that affect the strength of an electromagnet are

A

1, Investigate how the number of coils affects the number of paper clips attracted to the electromagnet-keep the current same in this experiment
2, Investigate how the size of the current affects the number of paper clips attracted to the electromagnet- keep the number of coils same in this experiment

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5
Q

Flemings Left hand rule

A

1, thuMb- Motion
2, First finger- magnetic Field
3, seCond finger- Current
They are all at right angles to each other.

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6
Q

How can the direction of the force acting on a wire in an electromagnetic field be reversed?

A
  • reversing the current

- reversing the magnetic field

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7
Q

What is an electric motor?

A

It is a device that converts electrical energy into mechanical energy to produce a turning effect.

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8
Q

What are most motors powered using?

A

Direct current, which is produced by cells and batteries.

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9
Q

What are most motors powered using?

A

Direct current, which is produced by cells and batteries.

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10
Q

What do motors powered by mains electricity use?

A

alternating current

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11
Q

Motors powered by mains electricity use

A

electromagnets rather than permanent magnets

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12
Q

What are the ends of a magnet called?

A

Poles

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13
Q

What two poles does a magnet have?

A

A north and south pole

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14
Q

What is the law of magnetism?

A

When two magnets are held close together, there will be an attractive or repulsive force between the magnets depending on how they are arranged.

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15
Q

Two like poles

A

repel each other

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16
Q

Two unlike poles

A

attract each other

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17
Q

The attraction or repulsion between two magnetic poles is an example of what force?

A

A non-contact force

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18
Q

What metals in the periodic table are magnetic?

A

Iron, nickel and cobalt

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19
Q

Steel

A

It is an allow that contains iron so is also magnetic

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20
Q

Are magnetic materials always attracted to the magnet?

A

Yes, regardless of the pole which is held close to it.

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21
Q

How do you test whether a material is magnetic?

A

It should be brought close to a known magnet.

  • if it can be repelled by the known magnet then the material itself is a magnet
  • If it can only be attracted and not repelled then it is a magnetic material
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22
Q

What are the two types of magnets?

A

Permanent and induced magnets

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23
Q

Permanent magnets

A
  • They are made out of permanent magnetic materials eg: steel
  • A permanent magnet will produce its own magnetic field. It will not lose its magnetism.
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24
Q

Induced magnets

A

-when a magnetic material is placed in a magnetic field,the material can be temporarily turned into a magnet

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25
Q

What happens when magnetism is induced on a material?

A
  • One end of the material will become a north pole

- The other end will become a south pole

26
Q

Magnetic materials will always be attracted to a

A

permanent magnet

27
Q

Since a magnetic material is always attracted to a permanent magnet, what does this mean?

A

This means that the end of the material closest to the magnet will have the opposite pole to the magnets pole closest to the material.

28
Q

What happens when a magnetic material is removed from the magnetic field?

A

It will lose all/most of its magnetism quickly.

29
Q

What are all magnets surrounded by?

A

A magnetic field

30
Q

What is the definition of a magnetic field?

A

The region around a magnet where a force acts on another magnet or on a magnetic material (such as iron, steel, cobalt and nickel).

31
Q

What are magnetic field lines used for?

A

They are used to represent the strength and direction of a magnetic field.

32
Q

How is the direction of a magnetic field shown?

A

Using arrows.

33
Q

How is the strength of a magnetic field shown by?

A

The spacing of the magnetic field lines

34
Q

If the magnetic field lines are close together,

A

the magnetic field will be strong

35
Q

If the magnetic field lines are far apart,

A

the magnetic field will be weak

36
Q

What are the rules which should be followed when drawing magnetic field lines?

A
  • They always go from north to south (indicated by an arrow midway along the line)
  • they must never touch or cross other field lines
37
Q

What is the magnetic field like around a bar magnet?

A
  • the magnetic field is strongest at the poles
  • This is where the magnetic field lines are closest together
  • the magnetic field becomes weaker as the distance from the magnet increases
  • This is because the magnetic field lines are getting further apart.
38
Q

What can an attractive force be experienced between?

A
  • The opposite poles of two different permanent magnets (due to the law of magnetism)
  • A magnet and a magnetic material (due to induced magnetism).
39
Q

Where is a uniform magnetic field produced?

A

In the gaps between opposite poles (it is not uniform outside that gap)

40
Q

What is a uniform magnetic field?

A

One that has the same strength and direction at all points

41
Q

How do you show that a uniform magnetic field has the same strength at all points?

A

There must be equal spacing (same distance apart) between all magnetic field lines.

42
Q

How do you show that a uniform magnetic field acts at the same direction at all points?

A

There must be an arrow on each magnetic field gong from the north pole to the south pole.

43
Q

A magnetic field is a

A

non-contact force. It is a region around a magnet where a force is experienced. It is a vector quantity (N–>S)- out of north into south

44
Q

How does a motor work?

A
  • the sides of the coal (parallel to the magnet) experience a force in opposite directions
  • the forces cause moments that act in the same direction/ the two halves of the commutator swap from one br
45
Q

F= BIL

A

B- magnetic field density- Teslas
I - current A
L- length m

46
Q

How do we know that the core of the Earth is magnetic?

A

A magnetic compass will always point north.

47
Q

What is produced when a current flows through a conducting wire?

A

A magnetic field is produced around the wire.

48
Q

How can the shape and the direction of a magnetic field be be investigated?

A

By using plotting compasses.

49
Q

What is a magnetic field made up of?

A

concentric circles.

50
Q

What does a circular field pattern indicate?

A

It indicates that a magnetic field around a current-carrying wire has no poles.

51
Q

As the distance from the wire increases, what happens to concentric circles of a magnetic field?

A

They get further apart.

52
Q

What do the concentric circles show about the magnetic field?

A

The magnetic field is strongest closest to the wire and gets weaker as the distance from the wire increases.

53
Q

What can be used to work out the direction of the magnetic field?

A

The right hand thumb rule

54
Q

Right hand thumb rule

A

Thumb- points along the direction of the current

other fingers give the direction of the field

55
Q

What will reverse the direction of the magnetic field (right-hand thumb rule)

A

Reversing the direction in which the current flows through the wire

56
Q

What does a circle with a dot in the centre show?

A

Current is flowing out of the plane.

57
Q

What does a circle with a cross in the centre show?

A

Current is flowing into the plane.

58
Q

When will there be no magnetic field?

A

If there is no current flowing through the conductor.

59
Q

What will increase the strength of the magnetic field?

A

Increasing the amount of current flowing through the wire.

60
Q

When does the motor effect occur?

A

It occurs when a wire with current flowing through it is placed in a magnetic field and experiences a force.

61
Q

What is the result of two magnetic fields?

A
  • One is produced around the wire due to the current flowing through it
  • the second is the magnetic field into which the wire is placed eg: between two magnets.

Physics GCSE (11 decks)

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