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Science Yr8 > Magnetism > Flashcards

Magnetism Flashcards

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1
Q

Is soft wood attracted to magnets?

A

no

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2
Q

Is nickel attracted to magnets?

A

yes

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3
Q

Is lead attracted to magnets?

A

no

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4
Q

Is matt steel attracted to magnets?

A

yes

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5
Q

Is iron attracted to magnets?

A

yes

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6
Q

Is bone attracted to magnets?

A

no

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7
Q

What are the only magnetic elements?

A

iron, cobalt and nickel

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8
Q

Are non-metals magnetic?

A

no

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9
Q

north + north

attract or repel?

A

repel

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10
Q

south + south

attract or repel?

A

repel

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11
Q

south + north

attract or repel?

A

attract

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12
Q

‘like’ poles …..

A

repel

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13
Q

‘unlike’ poles …..

A

attract

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14
Q

Does copper stop attraction?

A

no

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15
Q

Does nickel stop attraction?

A

no

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16
Q

Does iron stop attraction?

A

yes

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17
Q

Does cardboard stop attraction?

A

no

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18
Q

Where does the north seeking pole of a a magnet get attracted to? And where does the south-seeking pole of a magnet get attracted to?

A

The north seeking pole of a magnet gets attracted to the North Pole of the Earth and the south seeking pole of a magnet is attracted to the South Pole of the Earth.

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19
Q

what does the Earth behave like?

A
  • a massive bar magnet

- the North Pole of a magnet is attracted to the Eart’s north pole

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20
Q

How far is the magnetic North Pole from the geographical North Pole?

A

400km

11 degrees away from the rotational axis of the Earth

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21
Q

what does the Earth’s magnetic field do to keep us safe?

A

The Earth’s magnetic field deflects most of the sun radiation around the Earth. The Earth’s magnetic field protects us from harmful solar rays.
The magnetic field deflects much of the ionising radiation that comes from space and the sun

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22
Q

magnetic field:

A

the region around a magnet where it has a magnetic effect Is called its magnetic field

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23
Q

what happens if you put a magnetic material in a magnetic field?

A

it will experience a force and point from North to South on field lines

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24
Q

where do field lines go on a magnet?

A

north to south

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25
Q

do field lines touch?

A

no

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26
Q

where is a magnetic field strongest?

A

at the poles

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27
Q

what do magnetic field lines show?

A
  • shape of the field
  • direction of the field (N->S)
  • strength of the field
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28
Q

how do you show strong magnetic fields?

A

field lines close together

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29
Q

how do you show weak magnetic fields?

A

field lines are spread apart

30
Q

induced magnetism:

A

When a magnetic material is placed close to a magnet it becomes a magnet itself. This explains why magnetic materials are attracted to both poles of a magnet - they don’t have a magnetic orientation until they approach the magnet.

31
Q

non-magnetic material

A

-don’t have bar magnets or domains to line up because of a magnet

32
Q

magnetic material

A
  • has domains which line up because of a magnet but aren’t pointing in the same direction to begin with
  • don’t have a magnetic orientation
  • can only attract magnets
  • don’t have magnetic fields but are affected by magnetic fields
33
Q

magnet

A
  • when the domains stay lined up

- can repel and attract other magnets

34
Q

pure iron

A

pure iron is a soft magnetic material: its easy to magnetise but quickly loses its magnetism

35
Q

steel

A

steel is a hard magnetic material: it’s hard to magnetise, but retains its magnetism

36
Q

what happens when you stroke a needle with a magnet?

A
  • the domains line up and point in the same direction

- the domains would have previously been pointing in different directions

37
Q

What did Hans Christian Øersted do?

A

In 1820, he noticed that his compass changed direction whenever he ran an electric current.

38
Q

magnetic fields of electromagnets

A

If the wire is wound into a coil (called a solenoid) then the field is the same shape as a bar magnet

39
Q

what happens if the current is switched off in an electromagnet?

A

the magnetic field disappears

40
Q

domains in iron

A

has domains but are disordered

41
Q

How to make an electromagnet stronger?

A

3C’s

  • number of coils, directly proportional
  • increase voltage, directly proportional
  • core - iron core won’t stay magnetised when the current is turned off but steel will
42
Q

what happens to iron filings in a magnetic field?

A

the iron filings will feel the effect of the magnetic field and line up along the direction of the forces in the region

43
Q

what do field lines show?

A

the shape of the magnetic field

44
Q

What is Earth’s core made of?

A

molten iron

45
Q

magnetic poles switching

A

This is called a reversal and last happened 780,000 years ago. Weak and unstable fields are thought to precede magnetic reversals

46
Q

If like poles repel, why is the North Pole of a magnet attracted to the North Pole of the Earth?

A

These poles were named before magnetism was understood properly. The ‘magnetic North Pole’ of the Earth is really a magnetic South Pole.

47
Q

electromagnet

A

any wire with an electric current casing through it will produce a magnetic field

48
Q

use of electromagnets:

A

large, powerful electromagnets are used for lifting cars in recycling centres, steel works and scrapyards

49
Q

what does the strength of an electromagnet depend on?

A

whether it has a core of iron, the number of coils and the size of the current

50
Q

which way does the field move if the current goes up?

A

Flemings Law

anticlockwise

51
Q

which way does the field move if the current goes down?

A

Flemings Law

clockwise

52
Q

how do magnetic substance weaken magnetic fields?

A

by weakening the magnetic field

53
Q

what needs to be reduced to make a compass work properly?

A
  • friction at the pivots

- air currents

54
Q

how is a relay switch a safety measure?

A

it allows you to turn on a switch from a long way away

55
Q

What happens when the relay switch is switched on?

A
  1. The switch in the control circuit is closed.
  2. A small current flows through the control circuit.
  3. The electromagnet becomes magnetised and attracts the iron arm.
  4. The contacts in the floodlight circuit come together.
  5. A large current flows in the floodlight circuit.
  6. The floodlights come on.
56
Q

What happens when a relay switch is switched off?

A
  1. Switch in the control circuit is open.
  2. No current flows through the control circuit.
  3. Electromagnet is demagnetised and the iron arm swings back.
  4. The contacts in the floodlight circuit come apart.
  5. No current flows through the circuit.
  6. Floodlight turns off.
57
Q

how would you magnetise a needle?

A

by stroking the magnet in one direction along the needle

58
Q

what happens to a test tube full of iron filings as it becomes magnetised?

A
  • iron filings would have been spiky

- iron filings pointing in the same direction

59
Q

how would. you demagnetise something?

A
  • heat it till it was red hot

- put it in a demagnetising machine

60
Q

what sort of material blocks magnetic fields?

A

a magnetic-material

61
Q

The Earth is dawn on maps with North at the top. Which way round is the imaginary magnet inside the Earth?

A

South Pole at the top

62
Q

how do compass’s help travellers

A

it helps them navigate

63
Q

what happens to a compass in the Earth’s magnetic field?

A

it points to the North magnetic pole

64
Q

at the North Pole what direction does the compass show?

A

every direction shows the south

65
Q

why will a compass not work near an iron ship?

A

near an iron ship the iron in it attracts the compass needle

66
Q

why will a compass not work near the Cuillin Mountains in Scotland?

A

the rock contains magnetic iron ore which attracts the compass needle

67
Q

why will a compass not work near an electromagnet?

A

when the electromagnet is switched on it attracts the compass needle

68
Q

why would an electromagnet with a steel core not be useful for lifting cars?

A

steel retains its magnetism and its harder to be demagnetised

69
Q

Electric Bell

A
  1. when the switch is closed current starts to flow in the circuit
  2. the electromagnet switches on and develops a magnetic field
  3. the iron bar is attracted towards the electromagnet
  4. the arm swings up and hits the bell
  5. the circuit is ten broken and the electromagnet turns off
  6. the arm falls back down and the current starts to flow
70
Q

pivot

A

point of turn

71
Q

What happens if a current gets too large in a circuit breaker?

A
  • the iron lever will be attracted to the electromagnet as it will have a very strong magnetic field
  • the pivot and spring pull back the rod splitting apart the contacts
  • the circuit becomes incomplete
  • when the reset button is pushed the rod gets pushed back up and the iron lever falls onto the rod connecting the contacts again
72
Q

describing what happens inn circuits:

A
  • switch is closed
  • current flows through the circuit
  • electromagnet is turned on
  • it attracts something iron
  • something happens

Science Yr8 (26 decks)

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