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Physics > Magnetism and Electromagnetism > Flashcards

Magnetism and Electromagnetism Flashcards

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1
Q

What are the two poles on a magnet?

A

North pole and the south pole.

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2
Q

What do all magnets produce?

A

A magnetic field.

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3
Q

What is a magnetic field?

A

A region where other magnets or magnetic materials (e.g. iron, steel, nickel, cobalt) experience a non-contact force.

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4
Q

How can you show a magnetic field?

A

By drawing magnetic field lines.

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5
Q

What direction do the lines go and what do they show on a field line drawing?

A
  1. The lines always go from North to South.
  2. They show which way a force would act on a North pole if it was put at that point in a field.
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6
Q

If the lines are closer together, what does this mean?

A

The magnetic field is stronger.

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7
Q

The further away from a magnet you get, is the field strength stronger or weaker?

A

The field is weaker.

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8
Q

Where is the magnetic field the strongest?

What does this also mean to do with magnetic forces?

A

Its the strongest at the poles of the magnet.

This means that the magnetic forces are also strongest at the poles.

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9
Q

The force between a magnet and a magnetic material is always ……….. no matter the pole.

A

Attractive!!

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10
Q

If two poles of a magnet a put together, what will they exert?

What can they be?

A

They will exert a force on eachother.

Attractive or repulsive.

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11
Q

Will two of the same poles attract /repel?

A

Repel!!

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12
Q

Will two different poles attract or repel?

A

Attract!!!

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13
Q

What do you use to show the directions of magnetic fields??

A

A compass!

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14
Q

Explain how a compass works.

A
  • Inside a compass is a tiny bar magnet.
  • The north pole of this magnet is attracted to the south pole of any other magnet it is near.
  • Therefore the compass points in the direction of the magnetic field it is in.
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15
Q

How can you build up a picture of what a magnetic field looks like?

A

You can move a compass around a magnet and trace its position on some paper to build up a picture of what the magnetic field looks like.

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16
Q

When compasses are not near a magnet, where do they face?

Why??????

A
  • They always point north.
  • This is because the Earth generates its own magnetic field, which shows the inside (core) of the Earth must be magnetic.
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17
Q

What are the two types of magnets?

A
  1. Permanent magnets
  2. Induced magnets
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18
Q

What do permanent magnets produce?

A

They produce their own magnetic field.

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19
Q

What are induced magnets?

A

They are magnetic materials that turn into a magnet when they’re put into a magnetic field.

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20
Q

What is the force between permanent and induced magnets?

A

Its always attractive!!

21
Q

What happens when you take away the magnetic field with induced magnets?

A

Induced magnets quickly lose their magnetism ( or most of it) and stop producing a magnetic field.

22
Q

What does a moving charge create?

A

Magnetic Field!!!!

23
Q

When a current flows through a wire, what is created?

A

A magnetic field is created around the wire.

24
Q

Wire

What is the field made up of?

A

Concentric cirles perpendicular to the wire, with the wire in the centre.

25
Q

Wire

What happens when you place a compass near a wire that is carrying current and then you move the compass?

A

As you move the compass, it will trace the direction of the magnetic field.

26
Q

Motion with your hand the right hand rule!!

(Add pic)

A

need to add pic

27
Q

The strength of the magnetic field produced changes with the ……. and ……… from the wire.

A

Current and distance.

28
Q

When is the field stronger?

A
  • The larger the current through the wire.
  • The closer to the wire you are.
29
Q

What is a solenoid?

A

A coil of wire.

30
Q
  • How can you increase the strength of the magnetic field that a wire produces?
  • Why does this happen?
  • What does this result in?
A
  • By wrapping the wire into a coil called a solenioid.
  • Because the field lines around each loop of wire line up with each other.
  • This results in lots of field lines pointing in the same direction that are very close to each other. The closer the field lines are, the stronger the field.
31
Q

Whats the magnetic field like inside a solenoid?

A

Its strong and uniform, it has the same strength and direction at every point in that region.

32
Q

What is the magnetic field like outside the coil in a solenoid?

A

The magnetic field is just like the one round a bar magnet.

33
Q

What do the ends of a solenoid act like?

A

They act like the north and south pole of a bar magnet.

34
Q

How can you work out which end of the solenoid is the north pole and which is the south pole?

A

By using the right hand rule!

35
Q
  1. How can you increase the field strength of a solenoid even more?
  2. What does this become when current is flowing?
A
  1. By putting a block of iron in the centre of the coil.
  2. The iron core becomes an induced magnet whenever current is flowing.
36
Q

What happens when you stop the current in a solenoid with an iron core?

A

The magnetic field dissapears.

A solenoid with an iron core ( a magnet whose magnetic field can be turned on and off with an electric current) is called an ELECTROMAGNET.

37
Q

In bullet points, what is the motor effect?

A
  • When a current-carrying wire (or any other conductor) is put between magnetic poles, the magnetic field around the wire interacts with the magnetic field it has been placed in.
  • This causes the magnet and the conductor to exert a force on each other.
  • This is called the MOTOR EFFECT and can cause the wire to move.
38
Q

The motor effect

To experience the full force what does the wire have to be?

A

The wire has to be 90° to the magnetic field.

39
Q

The motor effect

Can the wire run parallel to the magnetic field?

A

If the wire runs parallel to the magnetic field, it won’t experience any force at all.

(At angles in between, it’ll feel some force.)

40
Q

The motor effect

The force always acts at 1)……… to the 2) ………..of the magnets and the 3) ………………. in the wire.

A

1) Right angles
2) Magnetic field
3) Direction of the current

41
Q

The motor effect

What is a good way of showing the direction of the force.

Explain this method.

A
  • Its to apply a current to a set of rails inside a horseshoe magnet.
  • A bar is placed on the rails which completes the circuit.
  • This generates a force that rolls the bar along the rails.
  • The magnitude ( strength) of the force increases with the amount of current passing through the conductor.
  • The force also increases with the amount of current passing through the conductor.
42
Q

What is the equation to find out the size of a force?

A

F= BI1

F= Force (N)

B= Magnetic flux density (T, tesla)

l = Current (A)

1= Length (m)

43
Q

The force acting on a conductor in a magnetic field depends on what three things?

A
  1. The magnetic flux density
  2. The size of the current through the conductor.
  3. The length of the conductor that’s in the magnetic field.
44
Q

What is the magnetic flux density?

What does this show?

A

How many field (flux) lines there are in a region.

This shows the strength of the magnetic field.

45
Q

How do you use Fleming’s left hand rule?

A
  1. Using your left hand, point your first finger in the direction of the magnetic field.
  2. Point your seCond finger in the direction of the Current.
  3. Your thuMb will then point in the direction of the force (Motion).
46
Q

What does Fleming’s left hand rule show?

What can this be used for?

A

It shows that if either current or the magnetic field is reversed, then the direction of the force will also be reversed.

It can be used for all sorts of things like motors.

47
Q

What coil of wire rotates in a magnetic field?

A

A current carrying coil of wire.

48
Q

need a pic of basic motor

A

Physics (5 decks)

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