  We study the thermal interaction between two nearby thin metallic wires, at
finite temperature. It is shown that the Johnson currents in the wires give
rise, via inductive coupling, to a repulsive force between them. This thermal
interaction exhibits all the puzzling features found recently in the thermal
Casimir effect for lossy metallic plates, suggesting that the physical origin
of the difficulties encountered in the Casimir problem resides in the inductive
coupling between the Johnson currents inside the plates. We show that in our
simple model all puzzles are resolved if account is taken of capacitive effects
associated with the end points of the wires. Our findings suggest that
capacitive finite-size effects may play an important role in the resolution of
the analogous problems met in the thermal Casimir effect.
