Electric potential(V) at a point is defined as the workdone by an electric field in bringing a unit positive
charge from infinity to that point.
The potential difference between two points A and B is defined as the workdone to take a unit positive charge
from Point A to point B
Electric potential V = KQ = W rq
Where K = 9.0 X 10⁹Nm²/c²
Q = q = net charge in C
r = distance in m
W = workdone in joules
Calculations
If two charged plates are maintained at a potential difference of 3KV. Calculate the workdone in taking a
charge of 600uC across the field.
solution
workdone = qV
where q = 600 x 10-6C
V = 3 x 1000v
W = 6 x 10-6 x 3 x 10³
W = 1.8J
A point charge of magnitude 2.5uC is moved through a distance of 0.04m against a uniform electric field of
intensity 15V/m. Calculate the workdone on the charge
solution
W = qV
but E = V/r
V = Er
:. W = q × E × r
Where q = 2.5 x 10 -6C
E = 15V/m
r = 0.04m
W = 2.5 × 10-6 × 15 × 0.04
W = 1.5 × 10-6J
Calculate the electric potential at a distance of 20cm from a point charge of 0.015C placed in permittivity.
(K = 9.0 × 10⁹Nm²/C²)
solution
V = KQ/r
where K = 9.0× 10⁹
Q = 0.015C
r = 20cm = 0.02m
V = 9.0 × 10⁹ × 0.015 0.02
V = 6.75 × 10⁸V