JEE PYQ: Magnetic Effects Of Current Question 9
Question 9 - 2021 (25 Feb 2021 Shift 1)
Magnetic fields at two points on the axis of a circular coil at a distance of $0.05$ m and $0.2$ m from the centre are in the ratio $8 : 1$. The radius of coil is
(1) $0.15$ m
(2) $0.2$ m
(3) $0.1$ m
(4) $1.0$ m
Show Answer
Answer: (3) $0.1$ m
Solution
$B = \frac{\mu_0 N i R^2}{2(R^2 + x^2)^{3/2}}$. Setting up the ratio and solving: $3R^2 = 0.03$, $R = 0.1$ m.
BETA
