4) shows how the electrostatic potential (  1/r) and the
electrostatic field ( 1/r 2 ) varies with r Example 2 1
(a) Calculate the potential at a point P due to a charge of 4 × 10–7C
located 9 cm away (b) Hence obtain the work done in bringing a charge of 2 × 10–9 C
from infinity to the point P