Household Circuits — Part 2: Wiring and safety: visual lesson, ICSE Class 10 Physics (Science Paper 1)

Lesson

From the power station to your socket

Part 2 — how electricity travels to a house, how the house is wired, and what keeps the people inside safe.

In this lesson you will

Describe how power reaches a house and the order of the parts from the pole to the circuits
Explain why switches and fuses go in the live wire; choose a fuse rating; compare a fuse and an MCB
Describe the ring main system, the two-way switch and the three-pin plug
Explain earthing, the colour code and electrical safety precautions

Table of four devices in the supply system and their jobs
Device	Job
Transformer	Changes the voltage
kWh meter	Records the energy used
Fuse or MCB	Cuts off an excess current
Earth wire	Carries a fault current safely to the ground

Concept

Power distribution

Power is generated at about 11 kV, stepped up to about 132 kV (or more) and sent along transmission lines. At substations it is stepped down in stages — to 33 kV, then 11 kV, then to 220 V at a local transformer — before it enters houses. Transmitting at a high voltage means a small current for the same power, so the heat lost in the lines, I²R, is far less.

Diagram

From the pole to the circuits

In order: pole → company fuse (in the live wire, sealed) → kWh meter (records units) → main switch (double pole: cuts both live and neutral) → distribution board with a fuse or MCB for each circuit. Separate circuits: lighting (about 5 A), power (about 15 A, for geysers and heaters) and the ring main. All appliances are connected in parallel, so each gets 220 V and works independently.

Cookies