Magnetism Flashcards
1
Q
Is soft wood attracted to magnets?
A
no
2
Q
Is nickel attracted to magnets?
A
yes
3
Q
Is lead attracted to magnets?
A
no
4
Q
Is matt steel attracted to magnets?
A
yes
5
Q
Is iron attracted to magnets?
A
yes
6
Q
Is bone attracted to magnets?
A
no
7
Q
What are the only magnetic elements?
A
iron, cobalt and nickel
8
Q
Are non-metals magnetic?
A
no
9
Q
north + north
attract or repel?
A
repel
10
Q
south + south
attract or repel?
A
repel
11
Q
south + north
attract or repel?
A
attract
12
Q
‘like’ poles …..
A
repel
13
Q
‘unlike’ poles …..
A
attract
14
Q
Does copper stop attraction?
A
no
15
Q
Does nickel stop attraction?
A
no
16
Q
Does iron stop attraction?
A
yes
17
Q
Does cardboard stop attraction?
A
no
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.
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
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
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
22
Q
magnetic field:
A
the region around a magnet where it has a magnetic effect Is called its magnetic field
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
24
Q
where do field lines go on a magnet?
A
north to south
25
do field lines touch?
no
26
where is a magnetic field strongest?
at the poles
27
what do magnetic field lines show?
- shape of the field
- direction of the field (N->S)
- strength of the field
28
how do you show strong magnetic fields?
field lines close together
29
how do you show weak magnetic fields?
field lines are spread apart
30
induced magnetism:
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
non-magnetic material
-don't have bar magnets or domains to line up because of a magnet
32
magnetic material
- 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
magnet
- when the domains stay lined up
| - can repel and attract other magnets
34
pure iron
pure iron is a soft magnetic material: its easy to magnetise but quickly loses its magnetism
35
steel
steel is a hard magnetic material: it's hard to magnetise, but retains its magnetism
36
what happens when you stroke a needle with a magnet?
- the domains line up and point in the same direction
| - the domains would have previously been pointing in different directions
37
What did Hans Christian Øersted do?
In 1820, he noticed that his compass changed direction whenever he ran an electric current.
38
magnetic fields of electromagnets
If the wire is wound into a coil (called a solenoid) then the field is the same shape as a bar magnet
39
what happens if the current is switched off in an electromagnet?
the magnetic field disappears
40
domains in iron
has domains but are disordered
41
How to make an electromagnet stronger?
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
what happens to iron filings in a magnetic field?
the iron filings will feel the effect of the magnetic field and line up along the direction of the forces in the region
43
what do field lines show?
the shape of the magnetic field
44
What is Earth's core made of?
molten iron
45
magnetic poles switching
This is called a reversal and last happened 780,000 years ago. Weak and unstable fields are thought to precede magnetic reversals
46
If like poles repel, why is the North Pole of a magnet attracted to the North Pole of the Earth?
These poles were named before magnetism was understood properly. The 'magnetic North Pole' of the Earth is really a magnetic South Pole.
47
electromagnet
any wire with an electric current casing through it will produce a magnetic field
48
use of electromagnets:
large, powerful electromagnets are used for lifting cars in recycling centres, steel works and scrapyards
49
what does the strength of an electromagnet depend on?
whether it has a core of iron, the number of coils and the size of the current
50
which way does the field move if the current goes up?
Flemings Law
| anticlockwise
51
which way does the field move if the current goes down?
Flemings Law
| clockwise
52
how do magnetic substance weaken magnetic fields?
by weakening the magnetic field
53
what needs to be reduced to make a compass work properly?
- friction at the pivots
| - air currents
54
how is a relay switch a safety measure?
it allows you to turn on a switch from a long way away
55
What happens when the relay switch is switched on?
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
What happens when a relay switch is switched off?
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
how would you magnetise a needle?
by stroking the magnet in one direction along the needle
58
what happens to a test tube full of iron filings as it becomes magnetised?
- iron filings would have been spiky
| - iron filings pointing in the same direction
59
how would. you demagnetise something?
- heat it till it was red hot
| - put it in a demagnetising machine
60
what sort of material blocks magnetic fields?
a magnetic-material
61
The Earth is dawn on maps with North at the top. Which way round is the imaginary magnet inside the Earth?
South Pole at the top
62
how do compass's help travellers
it helps them navigate
63
what happens to a compass in the Earth's magnetic field?
it points to the North magnetic pole
64
at the North Pole what direction does the compass show?
every direction shows the south
65
why will a compass not work near an iron ship?
near an iron ship the iron in it attracts the compass needle
66
why will a compass not work near the Cuillin Mountains in Scotland?
the rock contains magnetic iron ore which attracts the compass needle
67
why will a compass not work near an electromagnet?
when the electromagnet is switched on it attracts the compass needle
68
why would an electromagnet with a steel core not be useful for lifting cars?
steel retains its magnetism and its harder to be demagnetised
69
Electric Bell
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
pivot
point of turn
71
What happens if a current gets too large in a circuit breaker?
- 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
describing what happens inn circuits:
- switch is closed
- current flows through the circuit
- electromagnet is turned on
- it attracts something iron
- something happens
