Incandescent Bulbs: How They Work

How an Incandescent Bulb Works

Light bulbs work on a very simple principle. When metal is heated, it glows! The only problem is that it has to be heated up a lot.

Electricity comes into a light bulb via a hot wire connected to a tab on the base of the bulb. Inside the bulb the electricity goes through a wire leading to a piece of tungsten. The tungsten is very thin and coiled to maximize resistance in the wire. When electricity meets resistance, it heats up the resistor.

The tungsten gets to a temperature of about 4500° Fahrenheit (2482° Celsius). This causes it to get white hot. It glows, and glows quite brightly. Tungsten is used because it has a very high melting point.

The tungsten is encased in a bulb for good reason. Not only does it protect people and objects from the hot tungsten, it also keeps oxygen away from the hot metal, which would make it immediately burn up. The bulb is usually filled with a low pressure, inert gas such as argon.

After the electricity has made its way through the tungsten filament, it goes down another wire and out of the bulb via the metal portion at the side of the socket. It goes into the fixture and out a white wire.

Replacing a bulb is an easy matter of simply unscrewing a light bulb, then putting in a new one. (It is best if the switch is turned off when changing a bulb.) Replacing a light fixture can be a more complicated process.

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