Question

A point charge +Q is placed at point O, as shown in the figure. Is the potential difference V_A – V_B positive, negative or zero?

Answer 1

Electric potential at a distance r from the point charge +Q is given by

`V(r) = 1/(4πε_0) Q/R`

Potential at point A will be

`V(r_A) = 1/(4πε_0) Q/r_A`

Similarly, potential at point B will be 

`V(r_B) = 1/(4πε_0) Q/r_A`

`because r_A < r_B`

`therefore V_A > V_B`

`therefore V_A - V_B > 0`