Electrostatic force :

Electrostatic force is a conservative force. It’s an attractive or repulsive force between two electrically charged objects.

Potential at a point:

Potential at a point is the work done per unit charge (by an external agency) in bringing a charge from infinity to that point. If potential at infinity is chosen to be zero; potential at a point with position vector r due to a point charge Q placed at the origin is given is given by

The electrostatic potential at a point:

The electrostatic potential at a point with position vector r due to a point dipole of dipole moment p placed at the origin is
For a charge configuration  with position vectors  the potential at a point P is given by the superposition principle,
Where  is the distance between and P, as and so on.

Equipotential surface:

An Equipotential surface is a surface over which potential has a constant value.

Potential energy:

Potential energy stored in a system of charges is the work done (by an external agency) in assembling the charges at their locations.
Potential energy of two charges    at    is given by
Where is distance between .


A capacitor is a system of two conductors separated by an insulator. Its capacitance is defined by, C = Q/V
where, Q and –Q are the charges on the two conductors and
V is the potential difference between them.
The unit of capacitance is farad.

For a parallel plate capacitor (with vacuum between the plates).
Where A is the area of each plate and d is the separation between them.

Combination of Capacitors:

  • For capacitors in the series combination, the total capacitance C is given by

  • In the parallel combination, the total capacitance C is:
Where are individual capacitances.

Energy stored in Capacitor:

The energy U stored in a capacitor of capacitance C, with charge Q and voltage V is

The electric energy density (energy per unit volume) in a region with electric field is
Electrostatic potential Potential due to a point charge
Potential due to an electric dipole
Potential due to system of charges
Equipotential surfaces Properties
Relation between electric field and potential
Potential energy of a system of charges Potential energy of a single charge
Potential energy of a system of two charges in an external field
Potential energy due to dipole in an external field
Electrostatics of conductors Results of electrostatics of conductor
Dielectrics and polarisation Polar and non-polar dielectrics
Capacitors and capacitance
Capacitors and capacitance Parallel plate capacitor
Effect of dielectric on capacitance
Combination of capacitors Effective capacitance of two capacitors (a) in series combination and (b) in parallel combination
Energy stored in a capacitor
Numericals Concept based problems