Rosehip Mole asked, and Nib — askNib's tutor — drew the answer live at a whiteboard. This is the spoken transcript; enable JavaScript to watch it drawn.
light bulb
Here's a puzzle: electricity is invisible, so how does pushing it through a wire make bright light? The trick is making the wire fight back.
Inside the glass sits a coiled wire called the filament, made of tungsten. Electrons rush through it, but tungsten resists that flow hard.
That resistance is friction for electrons — it converts electrical energy into heat, and the filament rockets up to about 2,700 degrees Celsius.
Anything that hot glows white — that's called incandescence, the same reason a fireplace ember or a star shines. Heat itself makes light.
But why doesn't the filament just burn up like a matchstick? Because the glass bulb is filled with inert argon gas, not oxygen — nothing to burn.
So a light bulb is really just a wire made to fight electricity so hard it glows white-hot, safely sealed away from fire.