Question

Why does the connecting rod of an electric heater not glow while the heating element does?

Answer 1

An electric heater works on the principle of the heating effect of electric current.
The heating element of the heater blocks the electric current and does not let it pass. So the heating element gets heated and glows due the heat. It has high resistivity , so it does not melt. The cord of the electric heater is a good conductor of electricity so it does not get heated up and also does not glow.

Answer 2

because heating element and connecting are made from different elements.Heating element is generally made from Nichrome and connecting rod is from copper.

Nichrome has higher electrical resistivity than copper.so the heating element of heater glows but connecting rod does not.