CIE IGCSE Physics

Revision Notes

4.6.9 D.C. Motor

Simple D.C. Motor: Basics

  • The simple d.c. motor consists of a coil in a uniform magnetic field:

 

The electric motor, IGCSE & GCSE Physics revision notesThe simple d.c. motor

 

  • When there is a current in the coil, the magnets exert a turning effect on the coil, causing it to rotate
  • The force supplied by a motor can be increased by:
    • Increasing the current in the coil
    • Increasing the strength of the magnetic field
    • Adding more turns to the coil

 

Exam Question: Simple D.C. Motor

Extended Only

How a Simple Motor Works

  • When a current passes through the coil:
    • The current creates a magnetic field around the coil,
    • which interacts with the field of the magnets,
    • exerting a force on the coil,
    • in accordance with the left-hand rule
    • This pushes one side of the coil up and the other side down, causing it to spin
  • The commutator:
    • Reverses the direction of the current in the coil every half turn
    • This reverses the direction of the forces, which keeps the coil spinning

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