1. Safety Features in mains circuits

2. Household wiring  Use p268 to answer the following questions 1.Where is your electricity generated and how does it get to your house? 2.What do the letters L, N, and E stand for in wiring? 3.What is the function of the L, N, and E wires? 4.What does a.c. mean?

3. Learning Objectives  To know how electricity enters our homes  To know the functions of the wires in the UK mains electricity system

4. Mains Electricity  There are a large number of appliances which use mains electricity.  An appliance is a useful arrangement of electrical components.  These include cookers, heaters, lighting, TV, radio, hi-fi and computers.

5. UK mains electricity Supply  The UK mains electricity supply has three wires. They are called Live, Neutral and Earth and each wire has its own colour.  Live is Brown, Neutral is Blue, Earth is Green and Yellow stripes.

6. The live wire  The Live wire is connected directly to the generators of the electricity supply company.  NEVER touch this wire, it can kill you!

7. The Neutral Wire  The Neutral wire returns the electricity to the generator after it has passed through the appliance, to complete the circuit. NEVER touch this wire!!  In a complete circuit, it carries the same electricity as the Live wire.

8. The Earth Wire  The Earth wire usually carries no electricity, it is there as a safety device.  If something in the appliance goes wrong, or it is wired incorrectly, then the Earth wire carries the same electricity as the Live wire.  To be completely safe, NEVER touch this wire either

9. The Three Pin Plug

10. How to Remember  bLue goes LEFT  bRown goes RIGHT  sTriped goes to the TOP

11. A Mains Plug Complete your diagram and write down the function of each part of the plug

12. What is a fuse?  A fuse is a safety device which switches off an appliance if too large a current flows through the Live wire. The fuse is connected between the Live pin and the Live wire of a plug.

13. How does a fuse work?  The fuse has a rating printed on the outside in amps.  If the current going through the fuse rises above its rated value, then the fuse "blows" (it melts) which turns off the appliance.  For example, if the fuse says 5 amps, then a current greater than 5 amps will blow the fuse.

14. Fuses  The fuse breaks the circuit if a fault in an appliance causes too much ______ flow.  If the current going through the fuse is ______ than it’s rating then the wire heats up until it melts and ______ the circuit.  The fuse used should be rated at a current slightly _____ than the appliance normally uses

15. Power = Current x Voltage A vacuum cleaner has a rating of 460W on the 230 mains.A vacuum cleaner has a rating of 460W on the 230 mains. What fuse should be fitted in the plug?

16. Your task  Complete the ‘calculating which fuse to use’ sheet

17. Plenary  Write down any keys skills we have used during today’s lessons