Question

A uniform electric field E_0 is directed along positive y-driection. Find the change in electric potential energy of a positive test charge q_0 when it is displaced in this field from y_i=a to y_f=2a along the y-axis.

Answer 1

The change in electric potential energy is:

• A uniform electric field E₀ is directed along positive y-direction. Positive test charge q₀ is displaced in this field from y = a to y = 2a along y-axis.
• Work done in this process, W = - (Change in potential energy )

                                                     = F. d

• F = q₀ E
• d = displacement = 2a - a = a

• W = a q₀ E

• Change in potential energy = - W =  a q₀ E