# Coulomb’s LawCoulomb’s Law

Coulomb’s law can be applied to any point charges. It is given by:

Since ,  it follows that, for a point charge, the electric field strength is given by:

Gravitational and electric fields show some similarities and differences:

Gravitational                                                                         Electric

 Force is between Objects with mass Objects with charge Constant of proportionality G Applies to all materials ε depends on the medium in which the field exists Field strength in a radial field Nkg-1 or ms-2 Vector NC-1 or Vm-1 Vector Definition of Field Strength Force per unit mass Force per unit charge Force in a radial field Always attractive Vector Can be attractive or repulsive Vector Potential in a radial field Jkg-1 Scalar Always less than zero. JC-1 Scalar Sign depends on charges Definition of Potential Work done in bringing a unit mass from infinity to the point in the field. Work done in bringing a unit positive charge from infinity to the point in the field. Potential Energy Ep = Fm W=VQ