The light-emitting principle of incandescent lamps

2021-04-23 09:11:55 lighting 2

The origin of incandescent lamp

Thomas Alva Edison invented the incandescent light bulb in 1879 and is known as the father of light. But Edison was the one who invented and used the light bulb in the first place.

Thomas Alva Edison

Although the term "incandescent lamp" sounds very professional, it is actually a light bulb that is frequently used in modern life.

Structure diagram of light bulb

The structure of an electric bulb can be simply divided into three parts: the lamp cap, the wick, and the glass bulb. The structure of the wick is an important condition for light emission.

The wick is composed of 3 wires, which are A tungsten wire, C wire, and G wire. Among them, the A and G guide wires are copper guide wires and have relatively low resistance; while the resistance of the A tungsten wire is slightly larger.

When the current enters from the H solder joint, it passes through A, C, and G in turn. When the current reaches the tungsten wire with higher resistance, it starts to generate heat. After reaching a certain temperature, the tungsten wire will generate heat radiation and emit light.

The evolution of incandescent lamps

Earlier, Edison invented a carbon filament lamp (the raw material of A is carbon filament), which uses carbon filament to generate heat radiation and emit light, while tungsten filaments are used in modern incandescent bulbs.

At the same time, in order to protect the tungsten wire, the glass bulb was also evacuated and filled with nitrogen, which can make the life of the bulb a little longer.

This is the basic structure of the incandescent lamp and its light-emitting principle.

Why does the electric heater glow?

In fact, my friends can make an analogy: Everyone has used an electric heater in winter. When the electric heater is plugged in, it will become hot and red as the temperature rises. This phenomenon is caused by the increase in temperature that causes light.

Of course, since its temperature has not reached several thousand degrees, the light it emits is red.

From the perspective of physical energetics, the light-emitting principle of incandescent lamps is actually very simple. It is divided into two processes: firstly, electric energy is converted into heat energy (thermal effect); then heat energy is converted into light energy (heat energy will not be completely converted into light energy, there will be Some other consumption).

As the working temperature of the bulb increases, the heat radiation of the tungsten filament increases, and the visible light part also increases. Therefore, as the temperature of the electric heater gets higher and higher, the red light visible to our eyes becomes stronger and stronger.