Compact Fluorescent Lamp  Printable view
 
Fig. 1   There are many kinds of compact fluorescent lamps available on the market.

A normal incandescent light bulb is very hot when in use and with a working lifetime of only 750 to 1000 hours on average. That is why they need to be replaced quite frequently. In contrast, because compact fluorescent lamps (CFL) have a much longer life and operate at a much lower temperature, they help us to save energy and do not need replacing often. Sounds good? Work on the following activity to discover more advantages of using CFL.
 
Activity: Comparing a compact fluorescent lamp and an ordinary incandescent lamp

How can a CFL operate at such a low temperature and save so much energy? The answer lies in its fluorescent operation which is quite different from that of an ordinary light bulb.

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The operation of CFLs is very similar to that of fluorescent tubes. The advantage of a CFL is that it is compact and comparable in size to a regular light bulb; it can be used in most lighting fixtures.


Incandescent light bulb

The part of the light bulb that produces light is a long, thin and heavily coiled filament (usually made of tungsten), which is just a resistor coiled into a compact space. When you switch on the light bulb, current passes through the resistor and heats it up to a very high temperature, over 2000 oC. Because of this high temperature, the filament will glow and emit electromagnetic waves. A small part of the electromagnetic waves is visible light. Visible light is the part that is useful to us. At the same time, the filament also emits a large amount of invisible infrared radiation which carries away most of the energy from the light bulb. Infrared radiation can heat things, and that is why you feel very hot when you place your hand close to a light bulb. Light bulbs therefore have a low efficiency rate of about 5-10 % since most of their electrical energy is converted to heat instead of visible light.