This is evident from Equation (1), which is the relation between Joule’s law, Ohm’s law, and Pouillet’s law. (1) P=Across−section∗V2ρres,i∗lheater Here, P is the input power, Across−section is the cross-sectional area of the resistor, V is the input potential, ρres,i is the resistivity of resistor material i, and lheater is the length of the resistor.