The working principle of the incandescent lamp is that when the current passes through the filament (tungsten filament, melting point reaches more than 3000 degrees Celsius), it generates heat. The spiral filament continuously gathers the heat, making the temperature of the filament reach more than 2000 degrees Celsius. When the filament is in the incandescent state, it emits light just like the red iron can glow. The higher the temperature of the filament, the brighter the light. So it is called incandescent lamp. When incandescent lamps emit light, a large amount of electric energy will be converted into heat energy, and only a small part (perhaps less than 5%) can be converted into useful light energy.

Fluorescent lamp is also called fluorescent lamp. Its working principle: fluorescent lamp tube is simply a closed gas discharge tube. The main gas in the pipe is argon gas (excluding neon or krypton) with a pressure of about 0.3% of the atmosphere. In addition, it contains a few drops of mercury - forming trace mercury vapor. Mercury atoms account for about one thousandth of all gas atoms. The fluorescent lamp is the mercury atom of the lamp, which releases ultraviolet light (the main wavelength is 2537 angstroms=2537 × 10-10m）。 About 60% of the electricity consumed can be converted into ultraviolet light. Other energy is converted into heat energy.

Fluorescent lamps emit visible light after absorbing ultraviolet light by fluorescent substances on the inner surface of the lamp tube. Different fluorescent substances will emit different visible light. Generally, the conversion efficiency of ultraviolet light to visible light is about 40%. Therefore, the efficiency of fluorescent lamp is about 60% × 40%=24% - about twice the power of tungsten filament lamp.

Energy-saving lamp, also known as compact fluorescent lamp (CFL lamp for short in foreign countries), has the advantages of high light efficiency (5 times of ordinary bulb), obvious energy-saving effect, long service life (8 times of ordinary bulb), small size, convenient use, etc. Its working principle is basically the same as that of fluorescent lamp. Generally speaking, under the same wattage, an energy-saving lamp can save 80% energy than an incandescent lamp, extend the average life by 8 times, and the thermal radiation is only 20%.

LED lamp, also known as LED, is a solid-state semiconductor device that can directly convert electricity into light. LED lamps have many advantages such as small size, low power consumption, long service life, non-toxic and environmental protection. LED lamps have gradually developed from outdoor decoration, engineering lighting to household lighting.