When an incandescent light bulb is turned on, its thin wire filament heats up quickly. as the temperature of this wire filament increases, its electrical resistance ...

Well, we usually assume that the resistance of a circuit component

is constant and doesn't change. But the truth is that for anything

that conducts current, its resistance always increases somewhat

when it warms up.

For things like light bulbs, electric toasters, space heaters, electric

stove burners, the heat coils in a blow-dryer ... anything that's

designed to be really hot when it's doing its job ... the resistance

of those things increases significantly when they come up to their

operating temperatures.