Permanent & Induced Magnets (Edexcel IGCSE Physics)
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Permanent & induced magnets
Magnetic materials
Magnetic materials are attracted to a magnet; non-magnetic materials are not
Magnetic materials are materials which are attracted by magnets
Being a magnetic material does not mean the material is itself a magnet
Very few metals in the periodic table are magnetic, these include:
Iron
Cobalt
Nickel
Steel is an alloy which contains iron, so it is also magnetic
Magnetic materials will always be attracted to the magnet, regardless of which pole is held close to it
Magnetic materials attracted to either pole of a magnet
To test whether a material is a magnet it should be brought close to a known magnet
If it can be repelled by the known magnet then the material itself is a magnet
If it can only be attracted and not repelled then it is a magnetic material
There are two types of magnets
Permanent magnets
Induced magnets
Permanent magnets
Permanent magnets are made out of permanent magnetic materials, for example steel
A permanent magnet will produce its own magnetic field
It will not lose its magnetism
Induced magnets
When a magnetic material is placed in a magnetic field, the material can temporarily be turned into a magnet.
This is called induced magnetism
When magnetism is induced in a material:
One end of the material will become a north pole
The other end will become a south pole
Magnetic materials will always be attracted to a permanent magnet
This means that the end of the material closest to the magnet will have the opposite pole to magnets pole closest to the material
Inducing magnetism in a magnetic material
When the magnetic material is removed from the magnetic field it will lose most/all of its magnetism quickly
Worked Example
The diagram below shows a magnet held close to a piece of metal that is suspended by a light cotton thread. The piece of metal is attracted towards the magnet.
Which of the following rows in the table gives the correct type of pole at X and the correct material of the suspended piece of metal?
| Type of pole at X | Material of suspended metal |
|---|---|---|
A | North | Nickel |
B | South | Nickel |
C | North | Aluminium |
D | South | Aluminium |
Answer: A
X must be a north pole
The piece of metal is being attracted towards the magnet
The law of magnetism states that opposite poles attract
The material of the suspended piece of metal is nickel
Nickel is a magnetic material (It will experience a force when it is placed in a magnetic field, in this case it is attracted towards the magnet)
B is incorrect because X cannot also be a south pole (and hence is a north pole)
If the pole at X was a south pole then the piece of metal would be repelled from the magnet because the law of magnetism states that like poles repel
C and D are incorrect because aluminium is not a magnetic material
A non-magnetic material would be unaffected by the magnetic field produced by the magnet.
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