Given:
Magnitude of all three charges: q₁=q₂=q₃= q= 2.0 × 10^–7 C
Separation between first two charges: d = 20 cm = 0.2m

From the figure,
Distance between charge at A and both the charges:
r =10cm= 0.1 m
Distance between charge at b and both the charges:
r’= 20 cm= 0.2 m
Formula used:
Potential is given as
Here, Here, k is a constant and k= =9× 10⁹ Nm²C^-2 . q is the point charge and r is the distance between the charge and the point of influence.
Since A is midway between two point charges, potential at A will be due to both the charges:


Now, when charge at A is displaced to B, potential difference is created. Potential at B is due to both the charges at 0.2 m equally from B.
Potential at B:


Thus, Potential difference is:
V_A-V_B =36000-18000
∴ V_A-V_{B =} 18000
Work done is:
W= (V_A-V_B) × q
∴ W = 18000 × 2.0 × 10^-7
∴ W = 3.6 × 10^-3 J

Hence, 3.6× 10^-3 J of work is being done by the electric field during whole process.