Electrostatic Potential Energy

Electrostatic Potential Energy

When the forces between a system of particles are conservative, a potential energy function can be assigned to the system. When the system changes its configuration, the conservative force does some work and there is a change in potential energy of the system.

The charge in potential energy is defined as negative of work done by conservative force (or electric force) during the charge.

U_f - U_i = -W_cons = -W_e

If reference level of potential energy (datum) is taken, when the separation between the particles is infinite, then for a particular configuration having potential energy U,  is the work done by conservative force during the arrangement

U - 0 = -U = -

For examples:

1. A proton is fixed and an electron is moved from  to a point near the proton,  > 0  (  force and displacement are in same direction). This means U < 0, i.e. potential energy decreases.
   
   
    
2. A proton is fixed and another proton is moved from  to a point near it,  < 0U > 0
   
   
    
3. In figure (1), potential energy decreases as W_E > 0.
   In figure (2), potential energy increases as W_E < 0.
   In figure (3), potential energy decreases as W_E > 0.