Question

Why does the heating element of a heater become red hot, but the connecting wires remain cold?

Answer 1

The heating element is made of a high-resistivity alloy such as nichrome, while the connecting wires are made of copper, which has very low resistivity. Both carry the same current, and the heat produced is proportional to resistance (H = I²Rt). Therefore, the heating element produces much more heat and becomes red hot, whereas the copper wires produce negligible heat and remain cold.