When we have a number of point charges, to determine the force on a particular charge due to all other charges, we apply principle of superposition. If we have N number of charges Q₁,Q₂,.........Q_N located respectively at the points represented by the position vectors ,,...... , the force experienced by a charge Q located at is given by,

 .................................(2.3)

Electric Field

The electric field intensity or the electric field strength at a point is defined as the force per unit charge. That is

or, .......................................(2.4)

The electric field intensity E at a point r (observation point) due a point charge Q located at (source point) is given by:

..........................................(2.5)