A heat lamp is a powerful incandescent lamp used to produce heat. Although the incandescent lamp has been the standard for many years, it is slowly being phased out in favor of newer and more energy-efficient technologies. Nearly all the energy used in incandescent bulbs, after all, is turned into heat and not electricity. Since the heat lamp is used for its heat and not its light, this is actually seen as an advantage, and this light will be around for a long time to come.
Heat Lamp Basics
Heat Lamp Incandescence
The light bulb in a heat lamp has a thin filament surrounded by an inert gas. The filament is a resistor--a material that opposes the flow of electricity. When a current is run through the resistor, the resistor turns it into heat. The filament produces so much heat that it glows white hot. This is how heat lamps, and all incandescent lights work. The heat lamp is different in a few ways, however.
Heat Lamp Design
The biggest difference is the amount of power used. Most incandescent lamps are 100 watts or lower, but heat lamps generally run at 250 watts or more to generate more power. The bulb screws into a ceramic base instead of a plastic one so that the lamp doesn't melt from the heat. The heat lamp also has a reflector which directs the light and heat straight down, focusing it on whatever it is supposed to heat.
All objects create infrared light, and the hotter they are, the more infrared they produce. This infrared flows through the air like normal light, but warms any solid object is comes in contact with. Heat lamp bulbs are designed to produce the most infrared light possible. Many of them have red filters on them which block out all of the light that is not in the red to infrared spectrum. That light turns into heat, increasing the infrared radiation.