The formulation of field theory given previously suggests an alternative expression for the current density in quantum electrodynamics. This expression is gauge-invariant and conserved and differs from the usual current density by the divergence of a tensor which vanishes in the absence of a field. Corresponding to this current is a new electromagnetic field, which differs from the old only in the presence of particles. The energy density of this new field then contains the interaction energy of the magnetic moments of the particles with the magnetic field, together with some terms which are small for atomic electrons.