The element of heater is very hot while the wires carrying current are cold. Why?

Explanation

The element of heater is made of Nichrome which has high resistance, while the current carrying wires are made of copper (or aluminium) which has low resistance. In series the current is same, therefore by Joule’s law the heat produced `Q=r^2RT` depends only on resistance of the conductor. Hence the element of heater is very hot due to its high resistance and the lead wires, cold due to their low resistance.