A type A light bulb is the typical incandescent light bulb. It has a round top and a tapered bottom that allows it to be screwed into most light fixtures, and it can come in a brightness of 40, 60, 75 or 100 watts, although those wattages are being phased out in favor of lower-wattage, energy-efficient replacements with equivalent brightness.Continue Reading
The A in type A bulbs actually stands for "arbitrary spherical shape tapered to a narrow neck." The shape is most likely related to the shape of Thomas Edison's "first" light bulb, which needed to have the air vacuumed out in Edison's home or lab. The bulb also had to accommodate the filament, which produced light from the electricity that ran though it.
Though Edison is credited with making the first light bulb, there were actually a number of inventors trying to make them at the time, including Humphry Davy, who created the first electric light in 1802. Edison was simply the first to make a bulb that lasted as long as his did, with the ability to receive the energy from a centralized location for the sake of economy, but without the exorbitant expense of materials such as platinum, which is what Warren de la Rue used in 1840.Learn more about Lighting