The correct option is (a).
Explanation
The operation of electric heating appliances is based on the heating effect of electric current (Joule’s Heating). When electric current flows through a conductor, electrical energy is converted into heat energy, the magnitude of which is determined by the current, the resistance of the conductor, and the time for which current flows ($H = I^2Rt$).- Statement 1 is Correct: Heating elements are designed to have high resistance. When connected to an electric supply, the resistance opposes the flow of current, generating a significant amount of heat. This rise in temperature causes the element to glow, becoming red hot.
- Statement 2 is Incorrect: According to the laws of resistance, the resistance ($R$) of a wire is directly proportional to its length ($l$) and inversely proportional to its cross-sectional area ($A$). Since the heat produced ($H$) is directly related to resistance ($H \propto R$ for a given current), the amount of heat produced is dependent on the length of the wire.
- Statement 3 is Incorrect: A heating element is not typically a straight, thick copper rod. Copper is a good conductor with very low resistance, which would generate negligible heat and potentially cause a short circuit. Instead, heating elements are made of alloys like Nichrome (which has high resistivity and a high melting point) and are often coiled to increase the length of the wire within a compact space, thereby increasing resistance and heat generation.
Key Takeaway: Heating elements utilize materials with high resistivity and high melting points (such as Nichrome) to maximize heat generation via the Joule heating effect. The heat produced is strictly dependent on the dimensions (length and thickness) and material of the wire.