  We have considered a system of a metallic ring coupled to two electron
reservoirs. We show that in the presence of a transport current, the persistent
current can flow in a ring, even in the absence of magnetic field. This is
purely a quantum effect and is related to the current magnification in the
loop. These persistent currents can be observed if one tunes the Fermi energy
near the antiresonances of the total transmission coefficient or the two port
conductance.
