AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
Electromagnetism: An electromagnet is a solenoid with an iron core.
Wind a coil of wire around an iron bar, pass a current through it, and you have an electromagnet.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 7 of 9
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Wind a coil of wire around an iron bar, pass a current through it, and you have an electromagnet. Because the magnetic field only exists while there is a current in the coil, it can be switched on and off. Its strength can also be changed by altering the current, changing the number of turns, or adding an iron core, none of which is possible with a permanent magnet. That switchability is what makes electromagnets useful in devices like relays, electric bells, circuit breakers, and scrapyard cranes, where a load must be picked up and then released. Examiners often ask you to identify the core or explain how to increase the field strength.
What earns the marks
- Defining an electromagnet as a solenoid, or coil of wire, with an iron core.
- Stating that the magnetic field is present only while there is a current in the coil.
- Naming three ways of changing its strength: increasing the current, adding more turns to the coil, or adding an iron core.
- Explaining that an electromagnet can be switched on and off, unlike a permanent magnet.
Common mistakes and how to put them right
Defining an electromagnet as any coil of wire, omitting the essential iron core.
Saying an electromagnet is magnetic even when no current flows, rather than losing its magnetism.
Claiming an electromagnet cannot be switched off, confusing it with a permanent magnet.
Specifying a steel core for an electromagnet, which would remain magnetised.
Exam tips
- A complete definition needs all three parts: a coil, an iron core, and a current.
- State the main advantage over a permanent magnet as being able to switch the magnetic field on and off.
Try the lesson
The start of the Electromagnetism: An electromagnet is a solenoid with an iron core. lesson, made from checked teaching notes for this specification point.
Have a go first
Which material is used for the core of an electromagnet?
Listen
Wind a coil of wire around an iron bar, pass a current through it, and you have an electromagnet. Because the magnetic field only exists while there is a current in the coil, it can be switched on and off. Its strength can also be changed by altering the current, changing the number of turns, or adding an iron core, none of which is possible with a permanent magnet. That switchability is what makes electromagnets useful in devices like relays, electric bells, circuit breakers, and scrapyard cranes, where a load must be picked up and then released. Examiners often ask you to identify the core or explain how to increase the field strength. A strong answer earns marks for these points. defining an electromagnet as a solenoid, or coil of wire, with an iron core. stating that the magnetic field is present only while there is a current in the coil. naming three ways of changing its strength: increasing the current, adding more turns to the coil, or adding an iron core. explaining that an electromagnet can be switched on and off, unlike a permanent magnet. Exam tip: A complete definition needs all three parts: a coil, an iron core, and a current.
See it
Key words
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electromagnet
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switchable magnetism
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changing the strength
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uses in devices
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See every definition
- electromagnet
- A solenoid, or coil of wire, with an iron core, whose magnetic field is present only while there is a current in the coil.
- switchable magnetism
- The magnetic field exists only while there is a current in the coil, so it can be switched on and off, unlike a permanent magnet.
- changing the strength
- Its strength can be changed by increasing the current, adding more turns to the coil, or adding an iron core.
- uses in devices
- Its switchability makes it useful in devices like relays, electric bells, circuit breakers, and scrapyard cranes, where a load must be picked up and then released.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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