Question

why does the connecting cord of an electric heater not glow hot while the heating element does

Answer 1

the answers is, ideally the connecting cord has no resistance while heating element has some resistance, the resistance is oppose to flow of electrons, in side its like a acting the large force at one place, the resistance want to stop the flow of electrons(current), but voltage want to forcing to move of electrons , in this point it is generating heat at the heating element, but at the connecting cord has ideally no resistance to no at the cord
note: but the cord has very very low resistance even after some time you will feel hotness at the cord also

Answer 2

This is because resistance of cord of electric heater is less than the resistance of heating element. So more heat is produced in the heating element and less heat is produced in the cord.  Due to more heat, heating element glows