  It is shown that in a heterostructure where screening is eliminated, the
Amp\'ere-Maxwell law of electrodynamics implies that a dc or ac spinomotive
force can be inudced with a time rate of change of a transverse electric field,
and the magnetic analog of Amp\'ere law implies that a dc or ac spin current
can generate a transverse electric field at the same frequency outside the
spin-current channel. Both effects are quite weak but may be of some
usefulness.
