Q 12-06-049JEE MainJEE Main 2024 (5 Apr, Shift 1)Medium
Two conducting circular loops A and B of radii $a$ and $b$ respectively ($b \gg a$) are placed in the same plane with their centres coinciding. The mutual inductance between them is
Answer: (D) $\dfrac{\mu_0\pi a^2}{2b}$
Pass current $I$ in the large loop B. Its field at the centre is $\dfrac{\mu_0I}{2b}$, nearly uniform over the small loop A:
$$\phi_A = \frac{\mu_0I}{2b}\pi a^2 \Rightarrow M = \frac{\phi_A}{I} = \frac{\mu_0\pi a^2}{2b}$$
Solution by Sreeraj P, M.Sc Physics