Electric Potential on the surface of a charged spherical shell of radius shell of radius $10 \mathrm{cm}$ is $50$ volt. Find the value of electric potential at a distance of $20 \mathrm{cm}$ from the centre of spherical shell.

What does mean by energy stored in capacitor?

Prove that-

"The ratio of change in potentials of conductors after connecting two charged conductors in inversely proportional to their capacitances".

Draw a curve between electric field and distance for an uniformly charged non-conducting sphere.

Define:

$\left(\mathrm{b}\right)$ Equipotential surface.

Find the equivalent capacitance between points  $C$and $D$ in given figure.