Gravitational Field Electric Field Force is between Objects with mass Objects with charge Constant of proportionality GApplies to all materials ε depends on the medium in which the field exists Field strength in a radial field Nkg-1 or ms-2Vector NC-1 or Vm-1Vector Definition of Field Strength Force per unit mass Force per unit charge Force in a radial field Always attractiveVector Can be attractive or repulsiveVector Potential in a radial field Jkg-1ScalarAlways less than zero. JC-1ScalarSign 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