What is the concept?
An electric lamp is a device that produces visible light by the flow of electric current. An incandescent lamp produces light by a filament heated white-hot by electric current. Only 7-8% electricity turns into visible light while 90% or more turns into heat. Although the energy efficiency of electric lamp was low at that time, it started the first milestone in the world. Lamp life expectancy for modern types of lamp is usually 1000 hours of operation. A coiled filament of tungsten is commonly used in incandescent lamp at present.