The presence of an electric field, \(\vec E\), and a magnetic field,\(\vec B\), in matter results in a force density if the matter is charged and in a torque density if the matter carries electric and...The presence of an electric field, \(\vec E\), and a magnetic field,\(\vec B\), in matter results in a force density if the matter is charged and in a torque density if the matter carries electric and magnetic dipole densities. In addition, if the electric field varies in space (the usual case) then a force density is created that is proportional to the electric dipole density and to the electric field gradients.
