- If a current-carrying coil is placed in a magnetic field (As shown in the diagram above), a pair of forces will be produced on the coil. This is due to the interaction of the magnetic field of the permanent magnet and the magnetic field of the current-carrying coil.
- The diagram below shows the catapult field produced.
- The direction of the force can be determined by Fleming’s left-hand rule.
- Since the current in both sides of the coil flow in the opposite direction, the forces produced are also in the opposite direction. The 2 forces in opposite direction constitute a couple which produces a turning effect to make the coil rotate.
- Examples of electric equipment whose operation is based on this turning effect are
- the direct current motor
- the moving coil meter.