# 4.1.3 Magnets & Electromagnets

### Creating and Destroying Magnets

• Magnets are usually made from hard magnet materials
• There are several ways in which a magnet can be created:

Stroking with a magnet:

A magnetic material can be magnetised by stroking it with one end of another magnet

Using a direct current (d.c.) in a coil:

Placing a magnetic material in a coil and then passing a direct current through the coil will also magnetise it

Hitting with a hammer:

• If the material is placed in a magnetic field and then hit with a hammer, the material will also become magnetised

Hitting material placed into a magnetic field with a hammer can lead to the material becoming magnetised

Extended Only

### Methods of Demagnetisation

• Magnets can be demagnetised by using one of the following methods:
• Hit the material with a hammer (when it is not in a magnetic field)
• Heat the material (until it begins to glow) and then slowly let it cool
• Place the material in a coil containing alternating current (a.c.) and then slowly withdraw the material (with the a.c. power source still attached to the coil)

### Electromagnets

• When a current (d.c.) is passed through a long coil, the current creates a magnetic field around the coil similar to that of a bar magnet

The magnetic field around a solenoid (a long coil) is identical to the magnetic field of a bar magnet

• Placing a soft magnetic material (such as iron) inside the coil will make the field much stronger:
The coil becomes an electromagnet

An electromagnet consists of a coil of wire surrounding a soft iron core.

• Electromagnets have an advantage over ordering magnets as they can be turned on and off and the magnetic field strength can be changed
• The strength of an electromagnet’s magnetic field may be increased by:
• Increasing the current in the coil
• Adding more turns to the coil

#### Exam Tip

When discussing the strength of an electromagnet, avoid saying “add more coils”:
The coil describes the overall object – the individual loops of wire should be referred to as turns.
The correct phrase to use is “add more turns to the coil”.

### Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.
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