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Physics Paper 2 > Magnetism And Electromagnetism > Flashcards

Magnetism And Electromagnetism Flashcards

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1
Q

What are the two types of pole?

A

North and south

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2
Q

Where are the forces of a magnet strongest?

A

The poles

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3
Q

What sort of poles attract?

A

Unlike poles

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4
Q

What sort of poles repel?

A

Like poles

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5
Q

What sort of forces are attraction and repulsion between two magnet poles?

A

Non-contact forces

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6
Q

What is a magnetic field?

A

The region around a magnet, where a force acts on another magnetic or magnetic material.

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7
Q

What are some examples of magnetic materials?

A

Iron, steel, cobalt and nickel

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8
Q

What does the strength of a magnetic field depend on?

A

The distance from the magnet- it is strongest at its poles

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9
Q

What are permanent magnets?

A

Magnets that produce their own magnetic field.

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10
Q

What are induced magnets?

A

Magnets that become a magnet when placed in a magnetic field.

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11
Q

What does induced magnetism always cause?

A

A force of attraction

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12
Q

What happens when an induced magnet is removed from its magnetic field?

A

It loses most/all of its magnetism quickly.

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13
Q

What sort of force is always between a magnetic field and a magnetic material or an induced magnet?

A

One of attraction

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14
Q

Which direction should the arrows on field lines run?

A

From north to south

ANTS:
Away from north
Towards south

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15
Q

What do the arrows on field lines show?

A

The direction of the force that would act on a North Pole places at that point.

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16
Q

What sort of poles do induced magnets have?

A

Induced poles

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17
Q

What is flux density?

A

The density of field lines

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18
Q

What does the flux density indicate?

A

The strength of the field at that point- the closer together the lines, the higher the flux density.

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19
Q

What does a higher flux density do to the magnetic field?

A

The higher the flux density, the stronger the field and greater the force that would be felt by another magnet.

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20
Q

What sort of magnet does a magnetic compass contain?

A

A small bar magnet.

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21
Q

Why does the compass always point to the magnetic north?

A

Because the compass needle aligns with the Earth’s magnetic field and always points to the magnetic north. This proves that the Earth’s core must be magnetic.

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22
Q

How do you plot a field around a bar magnet?

A

1) Place the bar magnet on a piece of paper
2) Place the compass at one end of the magnet
3) On the paper, mark the point where the compass needle is
4) Move the compass so the tail of the needle is at the point that has just been marked
5) On the paper, mark a new point where the needle is
6) Repeat and connect the marks until the full field is plotted

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23
Q

How does an electromagnet work?

A

Whenever a current flows in a conducting wire, a magnetic field is produced around the wire.

24
Q

What does the direction of an electromagnetic field line depend on?

A

The direction of the current and can be found with the right hand grip method.

25
Q

How does the right hand grip method work?

A
  • Grip the wire in your right hand, with the thump pointing in the direction of the current.
  • The fingers curled around the wire will point in the direction that the field line should be drawn.
26
Q

What does the strength of an electromagnetic field depend on?

A

It depends on the size of the current and the distance from the wire.

27
Q

How can you test the strength of an electromagnetic field?

A

You can see the effect by placing a magnetic compass at different points along the wire whilst turning the power supply on and off.

28
Q

How is a solenoid formed?

A

A solenoid is formed when a wire is looped into a cylindrical coil.

29
Q

What does shaping a wire into a solenoid do to the strength of an electromagnetic field?

A

Shaping the wire into a solenoid increases the strength of a magnetic field, creating a strong uniform field inside the solenoid.

30
Q

What shape does the magnetic field around a solenoid form?

A

The magnetic field around a solenoid has a same sort of shape to that of a bar magnet.

31
Q

How do you increase the strength of the magnetic field around a solenoid?

A

By adding an iron core.

32
Q

What is an electromagnet?

A

A solenoid with an iron core.

33
Q

How does the solenoid increase the magnetic field strength?

A
  • It concentrates a longer piece of wire into s smaller area.
34
Q

What does the looped shape of a solenoid do?

A

It means that the magnetic field lines around the wire are all in the same direction.

35
Q

How can the north hand pole of a solenoid be found?

A

With the right hand grip method

36
Q

How do you use the right hand grip method to find the North Pole of a solenoid?

A
  • Hold the solenoid in your right hand with your fingers following the direction the current flows.
  • Your thumb will point to the North Pole of the solenoid.
37
Q

What are four examples of electromagnetic devices?

A
  • Scrap yard cranes
  • Circuit breakers
  • An electric bell
  • Within other circuits
38
Q

How does an electromagnet work in a scrap yard crane?

A
  • The crane operator lowers the electromagnet into a pile of steel and then switches on the electricity. This causes the steel disc to become a powerful magnet- the electricity magnetises the steel core.
39
Q

How does a circuit breaker work?

A
  • A circuit breaker works like a fuse. If the current in the electromagnet gets too strong it will attract the switch made up of iron. The circuit breaker protects the electromagnet and the current from getting too high.
40
Q

How does an electric bell work?

A

When the switch is pushed, the electromagnet is magnetised. The electromagnet attracts the iron arms and the hammer strikes the arm and breaks the circuit. The arm springs back, completing the circuit again and re magnetising the electromagnet. The cycle remains for as long as the button is pushed.

41
Q

How do electromagnets work within other circuits?

A

When the switch in the circuit is closed, it turns on the electromagnet which attracts the iron contact in the rocker. The rocker pivot closed the contacts, completing the second circuit.

42
Q

What is the motor effect?

A

When a current carrying conductor is placed in a magnetic, it experiences force.

43
Q

What is the motor effect caused by?

A

The field created by the current interacted with the magnetic field.

44
Q

How can the force in the motor effect be increased?

A

By increasing:

  • The size of the current
  • The length of the conductor in the magnetic field
  • The flux density
45
Q

What happens if you reverse the direction of the current or the magnetic field? (Motor effect)

A

It will cause the direction of the force to reverse.

46
Q

How can the direction of a conductor be found?

A

Using Fleming’s left hand rule.

47
Q

How does Fleming’s left hand rule work?

A
  • Hold the left hand so that the thumb, first finger and middle finger are all at right angles to each other.
  • Align the first finger so that it points in the direction of the magnetic field, from north to south
  • Rotate the wrist so that the second finger points in the direction the current is flowing
  • The thumb will be pointing i.e. the direction the conductor would move.
48
Q

In Fleming’s left hand rule what does the thumb represent?

A

The direction of the force?

49
Q

In Fleming’s left hand rule what does the index finger represent?

A

Magnetic field

50
Q

In Fleming’s left hand rule what does the middle finger represent?

A

The direction of the current.

51
Q

What can the left hand rule be used to find?

A

The direction of either the field, current or movement as long as the other two are known.

52
Q

Why will a current carrying coil in a magnetic field rotate?

A

Because the current giving up one side of the coil is in the opposite direction to the current coming down on the other side, so one side moves up and the other moves down.

53
Q

How does the design of an electric motor link to its functions?

A
  • it is designed so that the coil rotates continuously
  • brush contacts at the communicator ensure that the current direction in the coil is always in the same direction. This ensures that the motor continues rotating and does not simply stop in the upright position.
54
Q

How can fleming’s left hand rule be used in terms of electric motors?

A

It can be used on one side of the coil to work out which direction the motor will rotate.

55
Q

How do you make an electric motor rotate faster?

A

By increasing the current or magnetic field.

56
Q

How do you make a motor rotate in the opposite direction?

A

By reversing the current or magnetic field.

Physics Paper 2 (3 decks)

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