An electric heater and the connecting cord supplying it are both carrying the same current. The heating eleme…

Question

An electric heater and the connecting cord supplying it are both carrying the same current. The heating element glows red-hot, but the cord remains cool. Explain why, using the relevant physical law.

Accepted Answer

## Model Answer According to **Joule's law of heating**, heat produced is given by $H = I^2Rt$. Since both carry the **same current**, the heat produced depends on **resistance**. The heating element has **very high resistance**, so it produces much more heat and glows red-hot. The connecting cord has **very low resistance**, so negligible heat is produced and it stays cool. *Source: Chapter 11, Section 11.7 – Heating Effect of Electric Current* --- ## Explanation - The key law to quote is **Joule's law**: $H = I^2Rt$. - Since current $I$ is the same, the only variable is resistance $R$. - Examiners expect you to explicitly state that the heating element has **high resistance** and the cord has **low resistance** — this is the direct cause. - Don't write a long explanation; two crisp points earn full marks.

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