The heating element of an electric heater is made of an alloy which has a high resistance. When the current flows through the heating element, the heating element becomes too hot and glows red. The cord is usually made of copper or aluminum which has low resistance. Hence the cord doesn’t glow.

Introduction:
An electric heater consists of two main components: the heating element and the cord. The heating element, which is usually made of a resistive wire, converts electrical energy into heat energy. It glows when current passes through it due to its high resistance. On the other hand, the cord, which is typically made of a conductive material, does not glow. This can be explained by considering the properties of the materials used in each component.

Properties of the Heating Element:
The heating element in an electric heater is designed to have a high resistance. This high resistance allows it to generate heat when an electric current passes through it. When a current flows through a high-resistance wire, the wire experiences resistance heating. This heating effect causes the wire to reach high temperatures, leading to its glow. The heating element is typically made of materials such as nichrome, which have a high resistivity and can withstand the high temperatures generated.

Properties of the Cord:
Unlike the heating element, the cord of an electric heater is made of a conductive material, such as copper or aluminum. Conductive materials have low resistivity, which means they offer less resistance to the flow of electric current. As a result, the cord does not generate significant heat when current passes through it. The low resistance of the cord prevents it from reaching the high temperatures required for glowing.

Difference in Resistance:
The primary reason why the heating element glows while the cord does not is the difference in their resistances. The heating element is specifically designed to have a high resistance, which causes it to heat up and glow. In contrast, the cord has a low resistance, which prevents it from generating enough heat to glow.

Conclusion:
In conclusion, the heating element of an electric heater glows because it is made of a high-resistance material, such as nichrome, which generates heat when an electric current passes through it. On the other hand, the cord of the heater is made of a conductive material with low resistance, which prevents it from generating enough heat to glow. The difference in resistance between the heating element and the cord accounts for their different behaviors when current flows through them.