AC losses are numerically evaluated in superconductors with a rectangular cross section and an infinite length for the application of either transport current or external magnetic field perpendicular to the broadest face. It is assumed that the electromagnetic response is determined by Bean's critical state model, in which the critical current density is independent of the magnitude of local magnetic field. In this case, the AC loss per cycle can be estimated directly from the magnetic-flux distribution inside the superconducting wire at the peak of cyclic field. By investigating the influence of the aspect ratio of wire cross section on the losses, it is concluded that conventional expressions for a strip are almost applicable to a very thin but finite wire.
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