COULOMB’S LAW

Experiment has shown that a force exists between any two bodies that have a net electric charge, that is an excess of positive over negative charge or vice versa. When these bodies are at rest, these forces are called electrostatic. Such forces were studied by Coulomb who experimentally determined a law about them.
If two charges of magnitude Q1 and Q2 respectively are situated on bodies whose dimensions are small compared to the distance, R, between them:

• is proportional to Q1 Q2
• is inversely proportional to R2
• acts along the line joining the bodies, and
• is attractive or repulsive according to whether Q1 and Q2 are of unlike or like signs respectively. Thus the force experienced by Q2 due to the field of Q1 can be written as