The operation of energy-saving lamps is a mystery to many people. Why does it differ from that of an incandescent lamp? In the case of an energy-saving lamp, also known as CFL (Compact Fluorescent Lamp), the current goes through a tube that is filled with mercury vapour. When an electron of that current collides with a mercury atom, it may throw another electron out of orbit. During the relapse from this state to the basic state, energy is released in the shape of ultraviolet radiation. Ultraviolet radiation is invisible. A layer of powder is therefore applied to the inside of the glass wall of energy-saving lamps showing different kinds of fluorescence, thus converting UV radiation into warm, white light.
An energy-saving lamp has a built-in pre-switch device and starter, so that it does not need a special bracket and can be screwed directly into a fitting.