Read the following and answer the questions below.
In a hospital, engineers are setting up the domestic-type wiring for wards, where each ward has multiple electrical appliances connected in parallel. Each ward has two separate circuits — a 15 A circuit for high-power appliances such as geysers and air conditioners, and a 5 A circuit for lights and fans. The hospital also has machines that generate strong magnetic fields by passing large currents through coils.
(a) Why are the appliances in each ward connected in parallel rather than in series? [1]
(b) Why is a 15 A fuse used for the high-power appliance circuit instead of a 5 A fuse? [1]
(c) Give one reason why two separate circuits of different current ratings are used in the same ward. [1]
(d) What is the colour of insulation used for the earth wire in domestic wiring, and what is its purpose? [1]
Generated by claude-sonnet-4-6 · 2026-06-26 01:11 · grounding rag
Model Answer
(a) Appliances are connected in parallel so that each appliance gets the same potential difference (220 V) and can be operated independently. If one appliance is switched off, the others continue to work.
(b) High-power appliances like geysers draw large currents. A 15 A fuse allows this without melting, whereas a 5 A fuse would blow even during normal operation of these appliances.
(c) Two separate circuits are used so that high-power appliances (geysers, air conditioners) and low-power appliances (lights, fans) can be protected by fuses of appropriate current ratings, preventing damage due to overloading.
(d) The earth wire has green coloured insulation. It is connected to a metal plate buried in the earth and provides a low-resistance path for leakage current, protecting the user from severe electric shock.
Source: Chapter 12, Section 12.4 — Domestic Electric Circuits
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Explanation
- (a): The textbook explicitly states appliances are connected in parallel "in order that each appliance has equal potential difference." Also mention independent operation for full marks.
- (b): Link the answer to current rating — high-power appliances need higher current, so a higher-rated fuse is necessary for normal functioning.
- (c): The key idea is appropriate protection — different fuse ratings suit different appliances. Don't just say "safety"; be specific.
- (d): Examiners expect both: the colour (green) and the purpose (safety/low-resistance path/prevents shock). Missing either loses the mark.