Q. A circular coil $A\ $of radius$\ r\ $carries current$\ i.$ Another circular coil $B\ \ $of radius$\ 2r\ $carries current of$\ i.$ The magnetic fields at the centres of the circular coils are in the ratio of
A) 3 : 1
B) 4 : 1
C) 1 : 1
D) 2 : 1
Explanation
(d) $B_{1} = \frac{\mu_{0}}{4\pi}\ \frac{2\pi i}{r}\ \ \ and\ \ \ B_{2} = \frac{\mu_{0}}{4\pi}\ \frac{2\pi(i)}{(2r)} = \frac{\mu_{0}}{4\pi}\ \frac{2\pi i}{2r}$
$\therefore\ \ $ $\frac{B_{1}}{B_{2}}\ \ = \frac{2}{1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.