Not that long ago we had little choice in lighting our homes. That choice was the incandescent light bulb. It came in different light intensities and a few different bulb shapes. Technological advances in lighting now provide us with a variety of light bulbs and lamps (Figure 1). This article will attempt to explain the differences in the current products available.
Figure 1 - Collage of lamps & light bulbs
Figure 2 - Typical incandescent light bulb
The incandescent bulb is the most common bulb made and used around the world (Figure 2). It comes in a variety of bulb shapes, lamp bases, an assortment of colors, light intensities and life ratings.
The incandescent bulb is made up of a very thin piece of tungsten wire, called the filament, mounted in a glass globe that has a vacuum or inert gases, which are meant to extend the life of the filament as it heats and cools. When an electrical current is applied to the wire it glows, giving off light.
Incandescent bulbs are not an efficient producer of light versus the amount of energy required to give off the light. Most of the energy used to light an incandescent lamp is lost in heat. Because of the high energy consumption of incandescent bulbs many countries are planning on discontinuing their use over the next 3 to 5 years.
Some incandescent bulbs have multiple filaments allowing for a choice of light intensities.
The life of a standard incandescent lamp is approximately 1,000 hours, with budget bulbs lasting substantially less than 700 hours. Long life versions are available that last upwards of 5,000 hours.
Incandescent bulbs can be controlled with a standard dimmer.
Figure 3 - Typical halogen light bulb
A halogen light bulb (Figure 3) is based on the same technology used to make an incandescent bulb. The primary difference is that the glass bulb covering the filament contains a halogen/krypton gas mixture. Halogen bulbs last longer than a standard incandescent light bulb.
The use of halogen/krypton not only increases the life of the lamp, but it produces a brighter white light and uses less energy to create the same amount of light that an incandescent bulb uses.
Halogen bulbs produce a very high heat, in many cases the wattage can be used as a temperature measurement. e.g. a 300 watt bulb can easily be 300°C Because of the high heat, they have limitations to their placement. In areas such as kitchen's where temperatures are normally hotter than other rooms, the addition of halogen lamps can make the room much hotter. The bulbs must also be kept away from any flammable materials and where they might come in contact with humans.
The bulbs themselves must be handled carefully during installation to avoid any direct skin contact with the bulb itself, as this will have a negative affect on the lamps life.
Halogen bulbs can be controlled with standard dimmers.
Figure 3 - Typical fluorescent light bulb
Unlike a halogen or incandescent lamp a fluorescent bulb does not have a filament, nor does the glass do nothing more than encapsulate the filament. The glass covering, in the shape of a tube, holds a mixture of argon and mercury gases. When an electrical current is passed through the gas filled tube, it produces ultraviolet radiation which in turn causes a phosphorous coating which has been applied to the inside of the tube to glow and hence give off light.
Fluorescent lamps require additional electronics to make them work. These electronics are known as the ballast and are an integral part of the light fixture. It is the ballast that controls the noise level and inherent visual flickering of the fluorescent light fixture and determines whether or not the light fixture can be dimmed.
Fluorescent lamps are very efficient and give off little heat, they can be touched even when on. As well, the nominal life of a fluorescent lamp is 10,000 to 20,000 hours.
Initially fluorescent lamps did not produce color even close to natural sunlight. However, technology advances have allowed manufactures to produce fluorescent bulbs with excellent light characteristics.
The fluorescent lamp is designated with the letter "T", for tube, and a number, such as "T12". The number signifies the diameter of the bulb in 1/8 inches. e.g. a T8 bulb is 1 inch in diameter.