JAMB - Physics (1984 - No. 28)

The electromotive force obtained from a simple dynamo may be increased by

increasing the cross-sectional area of the coil

winding the coil on a soft-iron armature so as to decrease the magnetic flux through the coil

increasing the speed of rotation

making the field magnet longer

using low-resistance copper coils

Increasing the rotation speed enhances the electromotive force (EMF) generated due to Faraday's law of electromagnetic induction.