A connecting cord doesnt glow but a heating element does?
Cord consists of inner conducting wire of low resistance and outer cladding 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 very high resistance material.
The heat energy manifests as the increased temperature of the heating element, and the tempreature is so that the heat radiation falls in visible range, hence we see glowing heating element.
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