ELECTRIC HEATERS

are appliances for converting electrical energy into heat. This conversion depends on the fact that when an electric current flows through a conductor, heat is generated 4n an amount proportional to the product of the currents trength and the resistance of the conductor. There are two types of heaters, the radiant and the convection. The radiant heater depends upon radiation from the heating elements (maintained at approximately 1200° F.) to raise the temperature of the surroundings. The heating elements in this case are either large glow lamps with heavy filaments, or coils of resistance wire ports. A highly polished reflector is used to reflect and concentrate the heat rays into a ‘zone of action’. The heat generated, being radiant, only raises the temperature of a body opaque to the rays; it pa es through the air without heating it, effecting a rise of temperature of the air only by heating opaque objects, which in turn heat the air by conduction. This type of radiator is not well suited for general room heating, but is convenient for quickly warming a portion of the body. The convection heater consists of a resistance element in the form of a spiral spring, grid or flat strip of high resistance conductor, which is heated whenjcurrent flows through it. Operated at a much lower temperature than the radiant heated, it is so constructed that air circulates through the heating elements. Heated by contact with them, it rises, thus creating convection currents in the room. This type, well suited for ordinary heating service, is much used to heat electric cars, street railway waiting rooms, etc. Not with stand in the fact that electric heaters are 100% efficient, z.e. all the power consumed appears as heat, their use on a large scale is not commercially practicable. Thus, the cost of heating a house by electricity has been computed to be 200 times as great as by coal. This figure includes neither labor nor repairs. This disadvantage of these heaters is offset by their cleanline , convenience and the fact that they do not vitiate the air.