The heating of cables carrying current

The current carrying capacity of an insulated cable may be calculated from data on the thermal resistivity of the insulation and of the surface. It has been shown that such data may be obtained for any type of insulation from experiments on the cable itself, by applying a well-known method for determining heat conductivities. As a result of experiments on different types of cable insulation, the following values have been obtained for the thermal resistivities (deg. cent. per watt per inch cube).