20.4 - How the Electric Motor Works

Forces on a coil produce a turning effect

• A simple direct current (d.c.) motor is a coil of wire sitting between the poles of a magnet, free to turn on a spindle.
• When current flows, each side arm of the coil carries current in the opposite direction to the other.
• The motor effect pushes one side arm up and the other side arm down.
• These two forces act in opposite directions on opposite sides of the spindle, producing a turning effect so the coil rotates.

Making a motor turn faster

The turning effect on the coil is increased, making the motor turn faster, by:

• Increasing the current in the coil
• Increasing the number of turns on the coil
• Increasing the strength of the magnetic field

The motor effect:

• The side arms feel a force because they're current-carrying conductors at right angles to a magnetic field (the motor effect).
• The direction of each force is found with Fleming's left-hand rule.