Contents
Key Stage 3
Meaning
An electromagnet is a magnet made from a coil of wire wrapped around a soft iron core.
About Electromagnets
- Electromagnets only work when there is a direct current passing through the coil of wire.
- An electromagnet can be turned off and on.
- The strength of an electromagnet depends on; the number of coils of wire, the current through the wire and how easily the soft iron core can be magnetised.
- The more coils of wire the stronger the electromagnet.
- The greater the current through the wire the stronger the electromagnet.
- The more easily magnetised the soft iron core, the stronger the electromagnet.
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| The direction of the magnetic field can be changed by changing the direction of the current. |
Compared to a Bar Magnet
| Advantages of an Electromagnet over a Bar Magnet | Disadvantages of an Electromagnet compared to a Bar Magnet |
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Changing the current can change the strength of an electromagnet. An electromagnet can be turned on an off by turning the current on and off. The direction of the magnetic field can be changed in an electromagnet by changing the direction of the current. |
Electromagnets require a source of power to work. Electromagnets increase in temperature as they are used. |
Key Stage 4
Meaning
An electromagnet is a magnet made from a solenoid and a soft iron core.
About Electromagnets
- Electromagnets only work when there is a direct current passing through the solenoid
- An electromagnet can be turned off and on.
- The strength of an electromagnet depends on; the number of coils of wire in the solenoid, the current through the solenoid and how easily the soft iron core can be magnetised.
- The more coils of wire in the solenoid the stronger the electromagnet.
- The greater the current through the solenoid the stronger the electromagnet.
- The more easily magnetised the soft iron core, the stronger the electromagnet.
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| The direction of the magnetic field can be changed by changing the direction of the current. |
Compared to a Bar Magnet
| Advantages of an Electromagnet over a Bar Magnet | Disadvantages of an Electromagnet compared to a Bar Magnet |
|
Changing the current can change the strength of an electromagnet. An electromagnet can be turned on an off by turning the current on and off. The direction of the magnetic field can be changed in an electromagnet by changing the direction of the current. |
Electromagnets require a source of power to work. Electromagnets increase in temperature as they are used. |
Applications
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| When the switch is closed the electromagnet pulls the Iron armature towards it. This causes the the two large electrical contacts to touch. When the switch is open the electromagnet turns off and the contacts separate.
This is used for safety reasons so that a switch can be used to operate a circuit with a very large current indirectly. | |
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| When the switch is closed the electromagnet pulls the Iron armature towards it. This causes the a metal arm to bend and the striker to hit the bell. When the arm bends the circuit is broken and the electromagnet turns off. This allows the striker to move back away from the bell, where electrical contact is made and the process repeats. | |