In a circuit, would the electric field produced by emf instantly go to zero upon disconnecting the circuit from the emf source? I would assume there is some sort of time delay. If so, what is it? Similar question for a magnetic field: if a conducting solenoid producing a magnetic field is removed from its emf source, how fast would its magnetic field go to zero? I read something about magnetic field decay somewhere, and this article cites 30-thousandths of a second: http://newscenter.lbl.gov/news-releases/2013/04/30/antimatter-up-down/ Thanks.