Page 8 - Electrostatics-11

© GC Shiba
Electric potential: It is measured in terms of work done for which a reference

point is considered as infinity where potential is zero. (from Coulomb's law we
1
know that ∝ i.e., when → ∞, → 0).
2

Electric potential = [ ]
ℎ

or, = [ ]

Its SI unit is Volt (joule per coulomb) and CGS unit is stat volt.

1 volt = 1/300 stat volt

1 volt: Electric potential at a point in the electric field is said to be 1 V if 1 joule
work is done in a moving charge of 1 coulomb from infinity to that point.

Electrical potential at any point in the electric field is defined as the amount of
work done in taking unit positive charge (+1) from infinity to the point under

consideration.

P dr
⃗⃗
+Q
r (+1)

let us consider a point P in the electric field of +Q charge at a distance r. We
want to find electric potential at point P. Put +1 charge at point P.

The electric force acting at a point P between +Q and +1 according to Coulomb's
formula is

= Where is permittivity of the free space.
4 2 0
0
Now +1 charge is displaced by very small distance dr towards +Q charge then

⃗ ⃗⃗⃗⃗⃗
work done (dw) = .

= F dr cos180 0

= - F dr

= −
4 2
0

7 Electrostatics