A chamber heated to high temperature by electricity. The furnace consists of a refractory shell to resist the high temperatures attained within the chamber and minimize the heat losses to the surrounding area, plus a power source and electrical circuit to provide the heat. The operating temperatures range from a few hundred degrees Celsius to the melting points of refractory metals. The heating mechanism may be resistance, induction, microwave, or an electric arc in the largest installations. Electric furnaces are used primarily in the metallurgical industries for heat-treating, melting, and smelting operations. Resistance furnaces are used for heat treating. Induction furnaces are used to melt relatively low-melting alloys for casting, while arc furnaces are used for melting and smelting applications. The range of furnace powers, sizes, and geometries varies immensely. Powers range from a few kilowatts to 100 megavolt-amperes in a single unit. The furnace volume may be less than a cubic meter to more than 300 m³. Both cylindrical and rectangular geometries are common.