connected in the live wire, so that when the switch is open, the light is disconnected from the live wire.The lights are connected in parallel with each other, so that if one bulb fails the others are not affected.
SCIENCE,TECHNOLOGY & SOCIETY
Electricity at home When the live wire enters the house, it is first interrupted by the house’s main fuse and possibly a main switch. It then passes through a meter (similar to a joulemeter) which can measure the amount of electrical energy used (and records units used thus enabling your electricity provider to calculate customer costing). It then goes to the distribution box (sometimes called the junction box or fuse box).The neutral wire follows a similar route. From there the different circuits, explained above, carry electricity throughout the house.
Main fuse
L N
Meter Lights Ring circuit Cooker Distribution box 6A 30A 15A E
Radial circuit Fig 17.10:Typical domestic circuits The Kilowatt-hour (kW h)
1 kW h is the amount of energy used by a 1 000 watt appliance in one hour. It is the unit of electricity used by all electricity providers.
To calculate the cost of buying energy from all electricity providers, you multiply the number of kilowatt-hours by the price per unit by the time (in hours).
KILOWATT-HOUR energy (in kilowatt-hours) power (in kilowatts) time (in hours)
Power is defined as work divided by time.Work is the amount of energy transferred into or out of a system. It should therefore be clear that one way of describing the amount of electrical energy use would be to say it is power multiplied by time.The kilowatt-hour is thus a unit of energy as it is the product of units of energy and time.
The electricity meter records units used and enables the electricity provider to calculate customer billing. It is worth noting that it is usually cheaper to use electricity during ‘off- peak’ hours. Storage heaters make use of this by heating at night at the cheaper tariff, then releasing the stored heat (energy) during the day.
