The Motor Effect (Edexcel GCSE Combined Science) : Revision Note

The Force on a Wire

Higher Tier Only

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

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

The magnetic field between opposite poles of magnets interact with the magnetic field produced around a current-carrying wire

The motor effect is a result of two magnetic fields interacting to produce a force on the wire

Magnetic Forces

Higher Tier Only

• Magnetic forces are due to interactions between magnetic fields

  • Stronger magnetic fields produce stronger forces and vice versa

• For a current carrying conductor, 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 magnetic field between the poles of the magnet

  • Placing the wire at 90^o to the direction of the magnetic field lines between the poles of the magnet

    • This will result in the maximum interaction between the two magnetic fields

• Note: If the two magnetic fields are parallel there will be no interaction between the two magnetic fields and therefore no force produced