Hello all. I am currently studying electromagnetism with Griffiths' books, and I have already donde electrostatic and magnetostatics. Now I am reviewing Ohm's law en emf concepts, but I have a doubt: In griffths book, when explaining ohm's law and emf, it seems to me that he assumes steady currents and electrostatic fields. So, ohm's law is defined as J(r)=σE(r), and emf is defined as the closed line integral of the non electrostatic force acting on the circuit. But, what happens in non stationary conditions (time dependent elctric fields and currents)? Does Ohms law still remain the same? I mean, would this equation J(r,t)=σE(r,t) be correct? , and regarding emf, if electric field is not stationary anymore, would emf be defined in the same way? Regards.