A circular coil of N turns and diameter d carries a current I. It is unwound and rewound to make another coil of diameter 2 d, current I remaining the same. Calculate the ratio of the magnetic moments of the new coil and the original coil.

# A circular coil of N turns and diameter d carries a current I

**prasanna**#2

The length of wire will be same in two cases as the same coil is unwound and rewound.

Length of wire of coil 1 = Length of wire of coil 2