Question

why does the wire(cord) of electric heater not glow while heating element does

Answer 1

Cord is made up of an inner conducting wire of low resistance and an outer covering of insulating material. Since the conducting wire has low resistance, the electric energy is converted to heat to far less extent than in the heating element which is often a very high resistance material.

So,the heat energy shows as the increasing temperature of the heating element, and the temperature becomes so high that the radiation of the heat falls in our visible range, hence we see glowing heating element.

Answer 2

 The heating element of the heater is made up of alloy which has very high resistance so when current flows through the heating element , it becomes too hot and glows red. But the resistance of cord which is usually of copper or aluminium is very law so it doesn't glow.

Hope it helps...