Since Edison invented the electric lamp, the shape of the bulb has not changed much. Most of them are pear shaped. Now many people use energy-saving lamps. Energy-saving lamps not only save energy, but also look beautiful. They are available in all shapes. However, why are the incandescent bulbs we used to use made into pear shape instead of square, round or other shapes?
This is because the filament of the light bulb is made of tungsten with high melting point. After power on, the filament temperature is up to 2500 ℃, the filament heating reaches incandescent state and emits bright light. This kind of lamp is called incandescent lamp, which is different from the luminous principle of fluorescent lamp used in people's life. However, tungsten sublimates at high temperature, causing a small amount of tungsten particles to adhere to the inner wall of the bulb. As time goes on, the bulb will turn black and affect the lighting effect.
To this end, people fill the bulb with a small amount of inert gas that can insulate heat, and make the bulb into a pear shape. The gas generates convection and brings tungsten vapor to the pear shaped bulb neck for condensation and deposition, so as to keep the lower part of the bulb clean and keep the brightness unaffected. In addition, the pear shaped surface has a certain curvature, which can increase the strength and make the thin glass shell bear greater pressure, which is the same as that of egg shell.