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The Motor Effect


When a current flows through a wire a magnetic field is produced, although the field produced is weak. Coiling the wire increases the strength of the magnetic field.

 The strength of the magnetic field can be increased by the 3 C‘s;

  • having more Coils (turns) of wire
  • having more Current flow through the wire
  • having an iron Core

Electromagnets are used on cranes in scrap metal yards for lifting iron & steel.

The motor effect

When a current carrying wire is in a magnetic field it experiences a force. the size of the force experienced can be increased by;

  • increasing the strength of the magnetic field
  • increasing the current in the wire

If the wire is parallel to the magnetic field it does not experience a force.

Fleming’s Left Hand Rule

We use this to work out the direction of the force experienced by the wire.

Fleming's left hand rule 2

The direction of the force is reversed if either;

  • the direction of the current is reversed or
  • the direction of the magnetic field is reversed

The electric motor

The most useful application of the motor effect is in the electric motor. Electric motors are used in things like washing machines, electric cars, hair dryers, CD players etc.