The bulb is a non$-$ohmic resistor, that is$,$ it is not governed by the law of ohm. Doubling the potential difference at its terminals will not double the current passing through it$.$ The light emitted comes from a filament, a resistive element that heats to the point of emitting in the visible spectrum. This increase in temperature varies the value of the resistance. How does the resistance of the bulb vary with a greater electromotance? $($It increases, it decreases, does it remain the same?$\mathrm{)\; Explain.}$