How Do Light Bulbs Work?
Standard incandescent light bulbs work essentially the same way today that they did at the time of their invention over one hundred years ago. Thomas Edison is generally credited with inventing the light bulb in 1879, though Sir Joseph Swan of England arrived at the idea in 1878. Many inventors of the time were attempting to create a light source to replace candles and oil lamps that were not only dangerous, but dirty. By the turn of the century millions of households had replaced fire and oil with the humble electric light bulb. At the most basic level, light bulbs work by exciting atoms that release photons of light. Not all photons emit visible light, however. In fact because of the way light bulbs work, most of the radiation is emitted as heat rather than visible light. For this reason light bulbs are not very efficient generators of light by today’s standards. The modern light bulb is a thin, glass chamber filled with inert gases, usually argon. Two metal rods extend upwards into
The simplest light bulb, the one that screws into a lighting fixture, is called the incandescent lamp. If you can find one with a clear glass bulb, you will be able to see the parts inside. Two rather heavy and stiff wires lead up from the base. These are made of an alloy, a mixture of iron and nickel. They are called the leads. Stretched between them near the center of the bulb is a coil of smaller wire made of tungsten. This is the filament, the working part of the lamp. The bulb is designed to be screwed into a fixture that carries electricity at 120 volts. (That is standard for the wiring of homes in the United States and Canada.) When electricity to the lamp is turned on, the greatest resistance is in the tungsten filament. So the filament gets hot — hot enough that it glows and gives off light. In order to keep the filament from burning up, the air has been pumped out of the bulb and replaced with a mixture of argon and nitrogen.
1 Have you ever looked closely at a light bulb? At the bottom, there’s the bulb base. It has screw threads so it can be screwed into the light socket. At the very end, there’s a little bump. This makes contact with the electrical wires. The wires bring electricity to the bulb. When the bulb is screwed in and the light switch is turned on, electricity flows into the bulb. 2 Inside the glass bulb, there are glass rods coming up from the bulb base. There are tiny wires coming up from each side. At the top of these wires, a curly wire filament connects the two wires across the top. This curly wire filament is made of tungsten. Inside the glass bulb (although you can’t see it) is a kind of gas. It isn’t just the air we breathe. Air we breathe has oxygen in it. Oxygen will burn. The gas inside a light bulb is an inert gas. An inert gas will not burn or react in any way. Argon is the kind of gas used in most light bulbs. 3 When electricity flows into the bulb, it heats the tungsten wire filam
The simplest light bulb, the one that screws into a lighting fixture, is called the incandescent lamp. If you can find one with a clear glass bulb, you will be able to see the parts inside. Two rather heavy and stiff wires lead up from the base. These are made of an alloy, a mixture of iron and nickel. They are called the leads. Stretched between them near the center of the bulb is a coil of smaller wire made of tungsten. This is the filament, the working part of the lamp. The bulb is designed to be screwed into a fixture that carries electricity at 120 volts. (That is standard for the wiring of homes in the United States and Canada.) When electricity to the lamp is turned on, the greatest resistance is in the tungsten filament. So the filament gets hot hot enough that it glows and gives off light. In order to keep the filament from burning up, the air has been pumped out of the bulb and replaced with a mixture of argon and nitrogen. Our light bulbs are made by automatic machinery whic
