Coulomb's law

• Coulomb's law states any two charged particles exert a force on each other which is directly proportional to the product of their charges and inversely proportional to the square of their separation
• F = k *(Q*q/r^2)

  k = 1/4*pi*E0 therefore equations can be written as F = Q*q/4*pi*E0*r^2

  E0 = permittivity of air = 8.85*10-12
• Electric field strength around a point charge:

  E = F/Q rearranging F = Qq/4*pi*E0*r^2

  We get E = Q/R*pi*E0*r^2
• Electric Fields Gravitational fields

  The field can be attractive or Field is always attractive

  repulsive

  Obey inverse square law Obey inverse square law

  Both have radial fields