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.
Kindly refer to this link for similar answer.
https://www.meritnation.com/ask-answer/question/a-circular-coil-of-n-turns-and-diameter-d-carries-a-current/magnetism-and-matter/5919828