Why Does the Filament of a Light Bulb Glow While the Connecting Wires Do Not?
Incandescent Bulb Basics An incandescent light bulb is powered by an extremely thin filament of tungsten wire. As electricity flows through the wire, it heats up. As it heats up, the wire emits most of its heat as infrared radiation. Some of this heat energy, however, is actually emitted as the slightly higher frequency radiation we know as visible light. The connecting wires conduct electricity into the filament. They are deliberately kept relatively cool, since they are not inside the glass globe and unable to shine light into the room. Resistors and Conductors The tungsten filament is what is called a resistor–an electric component designed to resist the flow of electricity. That is one of the reasons why it is so thin. The thinner a wire, the harder it is for electricity to pass through and the more resistance the wire poses. The connecting wires, by contrast, are conductors–wires designed to carry electricity with as little resistance as possible. Their only purpose is to transp
