Heat is obtained from the electric current by placing a greater or less resistance in its path. Various forms of heaters have been employed. Some of the simplest consist merely of coils or loops of iron wire, arranged in parallel rows, so that the current can be passed through as many coils as are needed to provide the required amount of heat. In other forms the heating material is surrounded with fire-clay, enamel or asbestos, and in some cases the material itself has been such as to give considerable resistance to the current. A form of electric car heater is shown in Fig. 28. Forms of radiators are shown in Fig.. 21, 22 and 23, in Part I.

Fig. 26.

Fig. 27.