An incandescent Light Bulb is a device that produces light from the flow of current through a ‘tungsten” filament inside a sealed glass bulb, The tungsten filament is heated by electrical energy until it glows. The electrical energy is transformed to heat and then to light. In our homes these bulbs convert only about 5% of the electrical energy that runs through them into light. The rest comes out as heat.
A compact fluorescent light bulb (CFL) uses a technology that is four times as “efficient” as an “incandescent” bulb and lasts up to ten times as long. An ENERGY STAR qualified compact fluorescent light bulb (CFL) will save about $30 over its lifetime and pay for itself in about 6 months. It uses 75 percent less energy and lasts about 10 times longer than an incandescent bulb.
In a CFL, an electric current is driven through a tube containing argon and a small amount of mercury vapor. This generates invisible ultraviolet light that excites a fluorescent coating (called phosphor) on the inside of the tube, which then emits visible light.