An electric kettle is rated 230 V; 1000 W. Calculate the resistance of its heating element when in operation.
Generated by claude-sonnet-4-6 · 2026-06-15 06:43 · grounding rag
Model Answer
Given: V = 230 V, P = 1000 W
Using the formula $P = \dfrac{V^2}{R}$, we get:
$$R = \frac{V^2}{P} = \frac{(230)^2}{1000} = \frac{52900}{1000} = 52.9 \ \Omega$$
The resistance of the heating element is 52.9 Ω.
Source: Electric Power, Section 11.8, Chapter 11 – Electricity
---
Explanation
- Examiners expect you to state the formula used, substitute values, and arrive at the answer with units.
- The key formula here is $P = V^2/R$, rearranged to $R = V^2/P$. This comes directly from Section 11.8.
- Do not use $P = VI$ first to find current — it is an extra step and wastes time; the direct formula is cleaner and preferred.
- Always include the unit Ω in your final answer for full marks.