Electric potential energy is given by the formula 
This result is obtained by integrating the force-distance graph because work done is equal to the area under the graph.
Electric potential is the electric potential energy experienced per unit charge. Therefore, it is given by 
This result can also be obtained by integrating the electric potential-distance graph. Electric potential is defined as the work done in bringing unit positive charge from infinity to the point (electric potential is zero at infinity).
The electric p.d. between two points is simply the difference in potentials between them.
The capacitance of an isolated sphere can be easily derived:
