How does a light bulb work?

You flick a switch and — pop! — the whole room is bright. It feels like magic. But inside that little bulb, something clever and very fast is going on.

The switch joins the path

Electricity loves to travel along a path, like water along a pipe. This path is called a circuit. When the path is broken, nothing can flow and the bulb stays dark.

A switch is just a tiny gate in that path. Flick it up and the gate closes, joining the path so electricity can rush through. Flick it down and the gate opens, breaking the path. On, off, on, off!

Heat or LED — two ways to glow

Once electricity reaches the bulb, how does it make light? There are two main ways.

In an old-style bulb, the electricity flows through a very thin wire called a filament. The wire fights the electricity a little, which makes it get hotter and hotter until it glows white-hot and shines.

A modern LED bulb is cleverer. Inside are special little parts that turn electricity straight into light, almost without getting hot. That is why LEDs use far less power and last much, much longer.

Why we love LEDs now

Because they barely waste energy as heat, LED bulbs save electricity and rarely burn out. That is why most lamps today are switching to them.

Wonder fact: A glowing old-style bulb turns most of its energy into heat, not light — you could almost cook with one!