5.2.2Electricity and Magnetism
Induced Magnetism — Oxford AQA International GCSE Combined Science - Physics Revision Notes & Topical Questions
5 min read 7 parts Lesson 13 of 18
Part 1 of 5Magnetic materials
Only a few metals
- Only a few metals Very few elements are magnetic. The three magnetic metals are iron, cobalt and nickel.
- Steel is magnetic because it is an alloy containing iron.
Attracted to either pole
- Attracted to either pole A magnetic material that is not itself a magnet is attracted to both the north and the south pole of a magnet.
- It is not repelled by either pole.
Non-magnetic materials
- Non-magnetic materials Materials such as copper, aluminium, wood and plastic are not attracted to a magnet and are not repelled either.
Part 2 of 5Testing an unknown object
| Observation near a known magnet | Conclusion |
|---|---|
| Object is repelled | It is a magnet. Only a magnet can repel. |
| Object is attracted | It is a magnetic material (or possibly a magnet with opposite pole facing). |
| Object is neither attracted nor repelled | It is non-magnetic. |
| Repulsion seen when a pole is reversed | Confirms the object is a magnet, because repulsion is the only reliable test. |
Part 3 of 5Two kinds of magnet
Types of magnet
Permanent magnet
- Permanent magnet Made from a material that keeps its magnetism, such as steel.
- It produces its own magnetic field and does not lose its magnetism easily.
Induced magnet
- Induced magnet A magnetic material that becomes a magnet only while it is in a magnetic field.
- It is magnetised temporarily.
Key difference
- Key difference A permanent magnet can attract and repel.
- An induced magnet can only be attracted, and it quickly loses its magnetism when removed from the field.
Part 4 of 5How magnetism is induced
1
Bring a piece of magnetic material, such as an iron nail, close to one pole of a permanent magnet.
2
The magnetic field of the permanent magnet turns the nail into a magnet, with a north pole at one end and a south pole at the other.
3
The end of the nail nearest the magnet becomes the pole opposite to the pole it faces. A north pole induces a south pole, and a south pole induces a north pole.
4
Opposite poles attract, so the nail is pulled towards the magnet whichever pole is used.
5
When the nail is moved away from the magnet, it quickly loses most or all of its induced magnetism.
Part 5 of 5Why induced magnetism always attracts
1Field acts on the material
- Field acts on the material The magnet's field affects the magnetic material placed in it.
2Nearest end gets opposite pole
- Nearest end gets opposite pole The pole induced at the near end is always opposite to the pole of the magnet facing it.
3Opposite poles face each other
- Opposite poles face each other The two closest poles are unlike.
4Force of attraction
- Force of attraction Unlike poles attract, so the result is always attraction, never repulsion.
Key terms
| Term | Meaning |
|---|---|
| Magnetic material | A material, such as iron, cobalt, nickel or steel, that is attracted by a magnet. |
| Permanent magnet | A magnet that keeps its magnetism and has its own magnetic field. |
| Induced magnet | A magnetic material that is temporarily magnetised when placed in a magnetic field. |
| Magnetic field | The region around a magnet where a magnetic material feels a force. |
| Alloy | A mixture of a metal with other elements, for example steel containing iron. |
Avoid these mistakes
1
Saying that attraction proves an object is a magnet. Both a magnet and a magnetic material are attracted; only repulsion proves it is a magnet.
2
Believing all metals are magnetic. Only iron, cobalt, nickel and their alloys such as steel are.
3
Giving the wrong induced pole. The end nearest a north pole becomes a south pole, and vice versa.
4
Saying induced magnets can be repelled. Induced magnetism always results in a force of attraction.
5
Thinking that an induced magnet stays magnetic permanently once the magnet is taken away.
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