Question

what is the principal of dynamo

Answer 1

The principle, later called Faraday's law, is that an electromotive force is generated in an electrical conductor which encircles a varying magnetic flux. ... While current was induced directly underneath the magnet, the current would circulate backwards in regions that were outside the influence of the magnetic field.

Answer 2

the principle of dynamo is same as that of generator

.- when a coil is rotated in the magnetic field of a horseshoe magnet then current is induced in the circuit.

hope it helps