Abstract
The equation of motion for the sheet current in square and rectangular films with linear or nonlinear resistivity in a time dependent transverse magnetic field is presented. As examples, the linear susceptibility of rectangles with complex resistivity, the ideal diamagnetic moment, and the linear and nonlinear penetration of magnetic flux into high- Tc superconductors are given. The recently observed cushionlike flux penetration and the discontinuity lines in the current flow are confirmed.