1. The principal of the electric motorS

2. The principal of the electric motor
When the coil is vertical and no current is supplied to the motor inertia keeps it moving until the ends of the coil come into contact with the brushes again N S X N X N S
A current is supplied to the coil.
By Fleming’s LHR the coil rotates

3. The principal of the electric motorS X N
The coil has turned over and now the current though X is towards us and the coil continues to rotate
The cycle repeats again and again

4. Here you see the use of commutators to supply current to the coil when it is almost vertical

5. The simple motor can be used as a d.c. generator
This time turning the coil generates an e.m.f. as the coil cuts the lines of force of the magnet N S X N
E/V V π
2 π
3 π
Compare this with the a.c. generator