Revision Notes

4.6.7 Force on a Current-Carrying Conductor

The Motor Effect

  • When a current passes through a wire in a magnetic field, a force is exerted on the wire


The-motor-effect, IGCSE & GCSE Physics revision notesDiagram showing the force acting on a current-carrying wire in a magnetic field


  • The direction of this force depends on:
    • The direction of the field
    • The direction of the current
  • Reversing either of the above will reverse the direction of the force


Exam Question: The Motor Effect

Extended Only

The Left-Hand Rule

  • The force is always directed at 90 degrees to both the field and the current
  • The direction of the force on a current-carrying wire can be worked out by using the left-hand rule:


left-hand-rule, IGCSE & GCSE Physics revision notesThe left-hand rule can help you figure out the direction of the force on a current-carrying wire


  • Start by pointing your First Finger in the direction of the (magnetic) Field
  • Now rotate your hand around the first finger so that the seCond finger points in the direction of the Current
  • The THumb will now be pointing in the direction of the THrust (the force)


Exam Question: The Left-Hand Rule

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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