Q. The capacitance of a spherical condenser is 1 $\mu$F. If the spacing between two spheres is 1 mm, the radius of the outer sphere is
A) 3 m
B) 7 m
C) 8 m
D) 9 m
Explanation
(a) $r_{b} - r_{a} = 1mm = 10^{- 3}m\ $
From $\ \ \ \ \ C = \frac{4\pi\varepsilon_{0}r_{a}r_{\begin{array}{r}
b \\
\
\end{array}}}{r_{b} - r_{a}}$
$10^{- 6} = \frac{1\left( r_{b} - 10^{- 3} \right)r_{b}}{9 \times 10^{9}(10^{- 3})}$
$r_{b}^{2} = 9,\ r_{b} = 3m$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.