Question

Galvanometer having acquired resistance of 60 ohm shows full scale deflection when a current of 1 ampere passes through that it can be converted into an ammeter to read current of 25 ampere by

Answer 1

Adding a shunt resistance in parallel, of resistance 2.5 ohms.

At maximum deflection of the new ammeter, the current through the galvanometer must be 1A, so the current through the shunt must be 24A.

Since the shunt and galvanometer are in parallel, their potential drops must be equal. So:

S (shunt) * 24 = 60 * 1

S = 60/24 ohms = 2.5 ohms.