JEE PYQ: Magnetic Effects Of Current Question 19
Question 19 - 2020 (05 Sep 2020 Shift 1)
A square loop of side $2a$, and carrying current $I$, is kept in XZ plane with its centre at origin. A long wire carrying the same current $I$ is placed parallel to the $z$-axis and passing through the point $(0, b, 0)$, $(b \gg a)$. The magnitude of the torque on the loop about $z$-axis is given by:
(1) $\frac{\mu_0 I^2 a^2}{2\pi b}$
(2) $\frac{\mu_0 I^2 a^3}{2\pi b^2}$
(3) $\frac{2\mu_0 I^2 a^2}{\pi b}$
(4) $\frac{2\mu_0 I^2 a^3}{\pi b^2}$
Show Answer
Answer: (3) $\frac{2\mu_0 I^2 a^2}{\pi b}$
Solution
$\tau = MB\sin 90° = I(2a)^2 \times \frac{\mu_0 I}{2\pi b} = \frac{2\mu_0 I^2 a^2}{\pi b}$.
BETA
