  An attempt is made to explain the nature of the electric signal observed in
He II in a second-sound standing wave. Using the general quantum-mechanical
principles, we show that, due to interatomic interaction, each atom of He-II
acquires a small fluctuating induced dipole moment. A directed flux of
microscopic vortex rings -- which, together with phonons, are thermal
excitations of He II -- forms in the second-sound standing halfwave. This flux
partially orders the chaotically oriented dipole moments of the atoms, which
results in volume polarization of He II. The observed electric induction can be
explained theoretically under the assumption that each vortex ring possesses a
dipole moment of the order of ten atomic moments. It is shown also that the
theoretical value of the voltage U induced in He II by the volume system of
dipoles strongly depends on the dimensions of the resonator for dipoles of any
origin. The experimental value of U is the same for two resonators of different
size; therefore, this voltage may be not connected with the volume polarization
of He II.
