The Motor Effect (Oxford AQA IGCSE Physics): Revision Note

The Motor Effect

• The motor effect occurs when:

A wire with current flowing through it is placed in a magnetic field and experiences a force

• This effect is a result of two interacting magnetic fields

  • One is produced around the wire due to the current flowing through it

  • The second is the external magnetic field into which the wire is placed, between two magnets for example

• When the current-carrying conductor is placed in a magnetic field it cuts the lines of magnetic force

• As a result of the interactions of the two magnetic fields, the wire will experience a force

Magnetic fields interacting

Force on a current-carrying wire in a magnetic field

Factors affecting force

• The size of the force exerted by the magnetic fields can be increased by:

  • Increasing the amount of current flowing through the wire

    • This will increase the magnetic field around the wire

  • Using stronger magnets

    • This will increase the strength of the magnetic field between the poles of the magnet

  • Increasing the length of wire carrying current in the uniform field

    • A greater amount of magnetic flux is interacting so the force will be greater

• If the external magnetic field and wire are parallel there will be no interaction between the two magnetic fields and therefore no force produced