Question

In an electric field the work done in bringing at two column charge from infinity to a point a is standards and in bringing the same charge to the same point b is 20 joules find the potential difference between two points a and b what would be the work done if the same charge is brought directly from a to b

Answer 1

Work done = 10 joule

Charge = 2 coulomb

Potential of point A VA = 10 J / 2C = 5V

Given work done = 20 Joule 

     Charge = 2  coulomb

Potential of point A VB = 20 J / 2C = 10V

Potential differences between two point A and B is 

V = VB - VA

  = 10V - 5V = 5V

Work done directly from A to B.

Work done = Potential  difference × charge 

                    = 5V × 2C

                     10 Joule.