A household has a 15 A circuit for high-power appliances and a 5 A circuit for lights and fans. A student suggests connecting a 2 kW electric geyser (operating at 220 V) to the 5 A circuit since a socket is available there. Calculate whether this is safe and explain what would happen if the student went ahead.
Generated by claude-sonnet-4-6 · 2026-06-26 01:12 · grounding rag
Model Answer
Current drawn by the geyser:
$$I = \frac{P}{V} = \frac{2000}{220} \approx 9.1 \text{ A}$$
This exceeds the 5 A rating of the light-and-fan circuit, so it is not safe to connect the geyser there.
What would happen: The current (9.1 A) would exceed the circuit's 5 A limit, causing overloading. The fuse in the 5 A circuit would melt due to Joule heating, breaking the circuit to prevent damage to the wiring and appliances. If no fuse were present, the wires could overheat, potentially causing a fire.
Source: Chapter 12, Section 12.4 Domestic Electric Circuits
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Explanation
- Key formula: $I = P/V$ — examiners expect this calculation shown clearly.
- The 5 A circuit is meant for bulbs and fans, not high-power appliances like geysers (which belong on the 15 A circuit).
- Always link the conclusion to the fuse mechanism: excess current → Joule heating → fuse melts → circuit breaks. This is the core concept from Section 12.4.
- The word "overloading" must appear in your answer for full marks.