An inductor and resistor are arranged in parallel to a constant voltage source. There is a switch connected to a terminal on the inductor that can create a closed loop that includes either the voltage source, or the resistor. The switch is left connecting the source and inductor for a long period of time, then abruptly flipped to only connect the resistor and inductor. The magnetic field produced by the inductor goes from being zero, to some value that induces a current that will ensure a zero net current at the instant the switch is flipped. Is it possible for the magnetic field in the inductor to change instantaneously from 0 to B? No way! I feel there is an argument to be made which takes into account the propagation speed of the magnetic field (c), which means there is a finite amount of time that is required for the field to increase. I know it would be negligible, but I am just curious if there is some way to understand this seemingly "discontinuous" behavior. Any explanations or comments would be much appreciated.