Transcript Boardworks Electromagnets

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Magnetic effects of current
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Using electromagnets
A magnet created by electricity is called an electromagnet.
The magnetic field around an electromagnet is the same as
one around a bar magnet.
Unlike bar magnets, which are
permanent magnets, you can turn the
magnetism of electromagnets on and
off by closing or opening the switch.
Large, powerful electromagnets are
used for lifting cars in recycling
centres, steel works and scrapyards,
Why are electromagnets used instead of permanent magnets?
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Making an electromagnet
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Investigating electromagnets
The strength of an electromagnet depends on whether it
has a core of iron.
Two experiments can be carried out to investigate the other
factors that can affect the strength of an electromagnet:
 Investigate how the number of coils affects the number
of drawing pins attracted to an electromagnet – keep the
current the same in this experiment.
 Investigate how the size of the current affects the
number of drawing pins attracted to an electromagnet –
keep the number of coils the same in this experiment.
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Investigating electromagnets
How could you use the apparatus below to investigate the
effects of changing the current and the number of coils on
the strength of an electromagnet?
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Investigating electromagnets – results
Here are some example results:
number
of coils
number of
drawing pins
attracted
current
(A)
number of
drawing pins
attracted
0
0
0
0
20
8
1
12
40
18
2
23
60
31
3
38
80
46
4
49
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Investigating electromagnets – analysis
How did the number of coils affect the number of drawing
pins attracted to the electromagnet?
number of drawing pins attracted
50
40
30
20
10
0
0
20
40
60
80
100
number of coils
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Investigating electromagnets – analysis
number of drawing pins attracted
How did the size of the current affect the number of
drawing pins attracted to the electromagnet?
60
50
40
30
20
10
0
0
1
2
3
4
5
current (A)
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