# Why does increasing the voltage across and incandescent bulb increase its temperature?

I increased the potential difference across and incandescent bulb and noted the change in voltage and current, which, of course, changed proportionally. Why does increased voltage increase the temperature (and thus, the colour temperature) of an incandescent bulb? Does it cause more electron collisions and thus more energy is transferred to the lattice of the conduction filament, heating it up? And a further question on this, when photons are released, are they all within the visible light spectrum or do some contribute to thermal radiation as well?

Because incandescent bulbs produce light by virtue of being hot, and not through some other process like those used by other light bulbs. For a black body we know that the total amount of power radiated is:$$P \propto T^4.$$ While for a real object, like the wire in a light bulb, the relationship won't be exactly this, it will still follow that pattern that more power output (and thus, input) means higher temperature.