Magnets (Cambridge (CIE) IGCSE Co-ordinated Sciences (Double Award)): Revision Note

Temporary & permanent magnets

Types of magnets

• There are two types of magnets:

  • Permanent magnets

  • Induced (also called temporary) magnets

Permanent magnets

• Permanent magnets are made out of permanent magnetic materials, for example, steel

• A permanent magnet will produce its own magnetic field

  • It will not lose its magnetism easily 

Temporary (induced) magnetism

• An induced magnet is a material with a soft iron core that becomes a magnet temporarily when it is placed in a magnetic field

• When removed from the magnetic field, the material will lose its induced magnetism quickly and become unmagnetised

  • Some objects such as paperclips or needles (made from steel) can be magnetised and will remain magnetic for a while

  • Other objects, such as electromagnets or transformers (which are made from soft iron) will be unmagnetised (no longer magnetised) as soon as the cause of the induced magnetism is removed

Electromagnets

• An electromagnet can be made by winding coils of wire around a soft iron core

• An electromagnet can be switched on and off

  • When the current is flowing the electromagnet is switched on

  • When there is no current flowing then the electromagnet is switched off 

Electromagnet diagram

An electromagnet consists of coils of wire wrapped around a soft iron core

Differences between permanent and electromagnets

• There are many differences between permanent and electromagnets

  • These differences affect how these types of magnets are used

• Permanent magnets are always magnetic
  

  • They cannot be switched on and off

• Electromagnets are sometimes magnetic

  • An electromagnet is turned on by switching on the current passing through the coils of wire

  • The electromagnet is turned off by switching off the current

• It is not possible to change the strength of a permanent magnet

• The strength of an electromagnet can be changed in several ways:

  • By increasing the current

  • By increasing the number of turns of the coil

  • By adding a soft iron core

Uses of permanent and electromagnets

• Permanent and electromagnets have different uses

• Uses of permanent magnets include:

  • Compasses

  • School lab experiments

  • Toys

  • Fridge magnets

Some uses of permanent magnets

Compasses and toy trains are two examples of the use of permanent magnets

• Electromagnets have many uses including

  • MRI scanners

  • Speakers and earphones

  • Recycling

  • Mag-Lev Trains

Some uses of electromagnets

Picking and sorting scrap metal and an MRI scanner are two examples of the uses of electromagnets