Question

The ratio of magnetic field at the centre of a current carrying circular coil to its magnetic moment is 1.20 If the
current and radius both are doubled the new ratio will become?​

Answer 1

The new ratio becomes 1/8th of the former ratio.

That is,

New Ratio = 1.20/8 = 0.15

Hence, the answer is 0.15

PS:

For solution, see the attachment!