How does a light bulb work – for kids?
Have you ever looked closely at an ordinary electric light bulb?
Hold it carefully while you do so.
Inside, you may see wire “legs” holding up a thinner wire arranged in a coil.
When a light bulb is switched on, electricity flows along the thin wire and makes it glow.
Why does it glow white, and not red like the wire in an electric heater?
Why doesn’t the thin wire quickly burn out?
Many bulbs are filled mostly with argon gas. Because argon is inert, or chemically inactive, it allows the wire to glow brightly without burning.
If the bulbs were filled with air or oxygen, the wire would be destroyed by burning.
The wire glows white because it is so hot—over 4500°F (2482°C). And it doesn’t melt because it’s made of a metal called tungsten, which melts only at extremely high temperatures.
Gases in bulbs
Sometimes the gas inside a lamp produces a colored light.
Different gases glow in different colors. Street lights that shine yellow contain sodium as a gas. Neon gas glows orange-red, and krypton makes a greenish-yellow light. In fact, different mixtures of gases in special lamps can produce many different colors.
In these lights, the electricity doesn’t flow along a wire. It flows through the gas inside a thin, glass tube, making the gas glow. In a city at night, you can see lamps lighting up advertisements. These often flash on and off. Neon mixed with other gases gives them their different colors.
Halogen light is especially useful because it can be seen through thick fog. So it is often used in the warning lights at airports.
Xenon can be seen from long distances. That’s why the high-powered electric lamps used in some lighthouses may contain xenon. Xenon is helpful to photographers, too. It is the gas used in the tubes of electronic flash units.