Q 12-04-005NEETNEET 2025Top questionEasy
A $2$ amp current is flowing through two different small circular copper coils having radii ratio $1:2$. The ratio of their respective magnetic moments will be
Answer: (A) $1:4$
Magnetic moment of a coil: $m = NIA = NI\pi r^2$. With the same current (and the same number of turns),
$$\frac{m_1}{m_2} = \frac{r_1^2}{r_2^2} = \left(\frac{1}{2}\right)^2 = \frac{1}{4}$$
Solution by Sreeraj P, M.Sc Physics