A spark plug in a car has electrodes separated by a gap of $0\mathrm{.}0635$ cm$.$ To create a spark and ignite the air$-$fuel mixture in the engine, an electric field of $3\mathrm{.}0$x$106$V$/$m must be present in the gap. What potential difference must be applied to the spark plug to initiate a spark? If the separation between the electrodes is increased, does the required potential difference increase, decrease or stay the same?$$