Page 1 - Lesson Note - 1

Class XII

PHYSICS

Ch-2 Electric Potential & Capacitance

LESSON NOTES

1. Electrostatic Potential The electrostatic potential at any point in an electric field is equal to the
amount of work done per unit positive test charge or in bringing the unit positive test charge from
infinite to that point, against the electrostatic force without acceleration.

NOTE: Electrostatic potential is a state dependent function as electrostatic forces are conservative
forces.
2. Electrostatic Potential Difference The electrostatic potential difference between two points in
an electric field is defined as the amount of work done in moving a unit positive test charge from
one point to the other point against of electrostatic force without any acceleration (i.e. the
difference of electrostatic potentials of the two points in the electric field).

where, is work done in taking charge q0 from A to B against of electrostatic force.
Also, the line integral of electric field from initial position A to final position B along any path is
termed as potential difference between two points in an electric field, i.e.

NOTE: As, work done on a test charge by the electrostatic field due to any given charge
configuration is independent of the path, hence potential difference is also same for any path.
For the diagram given as below, potential difference between points A and B will be same for any
path.

3. Electrostatic potential due to a point charge q at any point P lying at a distance r from it is
given by

4. The potential at a point due to a positive charge is positive while due to negative charge, it is
negative.
5. When a positive charge is placed in an electric field, it experiences a force which drives it from
points of higher potential to the points of lower potential. On the other hand, a negative charge
experiences a force driving it from lower potential to higher.
6. Electrostatic potential due to an electric dipole at any point P whose position vector is r w.r.t.