Helo all. Stationary currents are those whose current density is constant in time. On the other hand, ohm law claims that in certain materials, current density is proportional to electric field within the material. So, if the electric field is stationary (constant in time), the current density must be constant in time, and the current stationary. But, in the case of a non stationary electric field, the current density should be time dependent, and the current producen should be non stationary. Is it right? And a second question. Does the ohm law for currents and potential difference holds in the case of non stationary currents? If so, is the resistance fórmula for a piece of conducting material holds for non stationary currents? Thanks all!