Video explanation
Closing the switch sends current through a filament that heats and glows. Introducing air demonstrates burning and damage, followed by an exploded view.
Resistive heating
Current through the resistive filament converts electrical energy into heat, producing visible thermal radiation at high temperature.
Limiting oxidation
Early carbon-filament lamps evacuated air to reduce oxidation of the hot filament and prolong operation.
Brightness and lifetime
Higher temperature can increase brightness but also material loss. Displayed temperatures and lifetime changes are illustrative.