Magnetism (Cambridge (CIE) IGCSE Co-ordinated Sciences (Double Award)): Revision Note
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Magnetism
Magnetic and non-magnetic materials
Very few metals in the Periodic Table are magnetic
The magnetic metals are:
Iron
Cobalt
Nickel
Steel is an alloy which contains iron, so it is also magnetic
Magnetic materials
Magnetic materials are attracted to a magnet; non-magnetic materials are not
Magnetic materials (which are not magnets) will always be attracted to the magnet, regardless of which pole is held close to it
Magnets and magnetic materials
Magnetic materials are attracted to both poles of a permanent magnet
Bringing a material close to a known magnet will determine if the material is magnetic, non-magnetic or if it is a magnet itself
It is a magnet if it is repelled by the known magnet
It is a magnetic material if it is attracted to the known magnet
It is a non-magnetic material if it is neither attracted nor repelled by the known magnet
Forces between magnetic poles
The ends of a magnet are called poles
Magnets have two poles: a north and a south
Magnetic forces are strongest at the poles
North and south poles of a magnet
Poles of a Magnet
When two magnets are held close together, there will be a force between the magnets
Like poles repel (push each other apart)
A north pole will repel a north pole
A south pole will repel a south pole
Opposite poles attract (are pulled toward each other)
A north pole will be attracted to a south pole
Magnet attraction and repulsion
Opposite poles attract and like poles repel
Forces between magnets and magnetic materials
When there is a force of attraction between a magnet and a magnetic material the magnetic material has been magnetised
This means that the end of the material closest to the magnet will have the opposite pole to that of the magnetic pole closest to the material
When removed from the magnetic field, the magnetic material will lose its induced magnetism quickly and become unmagnetised
Forces between magnets and magnetic materials
Induced magnetism causes a magnetic material to become magnetised where the poles act like the poles of a magnet.
Examiner Tips and Tricks
In your exam, you need to be able to predict the interaction that will occur between magnets when given their physical arrangement.
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Induced magnetism
Extended tier only
An induced magnet is a material with a soft iron core that becomes a magnet temporarily when it is placed in a magnetic field
Induced magnetism always causes a force of attraction between a magnet and an induced magnet
When this happens it is said that the material has been magnetised
Induced magnetism in a magnetic material
Inducing magnetism in a magnetic material
Worked Example
The diagram below shows a magnet held close to a piece of metal 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 piece of 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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