A circular loop and a square loop are formed from two wires of same length and cross section. Same current is passed through them. Then the ratio of their dipole moments is

Options

A. 4
B. `2/pi`
C. 2
D. `4/pi`

Answer

D

Explanation

The ratio of dipole moments,
`(M_(1))/(M_(2))=(ipir^(2))/(ia^(2))=(pi(l/2pi)^(2))/((l/4)^(2))=pi(16)/(4pi^(2))=(4)/(pi)`