Question

The respective radii of the two spheres of a spherical condenser are $12cm$ and $9cm$. The dieletric constant of the medium between them is $6$. The capacity of the conderser will be

• A. $240pF$
• B. $240\mu F$
• C. $240F$
• D. None of the above

Answer 1

The correct option is A $240pF$

Capacitance of spherical condenser of inner radii $a$ and outer radii $b$ is $C=4\pi {\epsilon }_{0}K\left[\frac{ab}{b-a}\right]$

Here $b=12cm,a=9cm,K=6$

$C=\frac{1}{9\times {10}^9}\times 6\times \left[\frac{12\times 9\times {10}^{-4}}{3\times {10}^{-2}}\right]$
$C=24\times {10}^{-11}=240pF$