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Physics

Physics. Electricity in the home. What is direct current (d.c.)?. Direct current ( d.c .) is an electric current that always flows in one direction. Made by batteries. Electronic circuits such as those in computers and stereos need direct current electricity in order to work.

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Physics

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  1. Physics Electricity in the home

  2. What is direct current (d.c.)? Direct current (d.c.) is an electric current that always flows in one direction. Made by batteries. Electronic circuits such as those in computers and stereos need direct current electricity in order to work. Direct current cannot be transferred well over large distances.

  3. What is alternating current (a.c.)? Alternating current (a.c.) is an electric current that is constantly changing direction. produced by most generators and is used in mains electricity. Motors often work using alternating current. The voltage of alternating current is easily changed with a transformer. Alternating current can be transferred efficiently over large distances.

  4. Which type of current – a.c. or d.c.?

  5. Electricity supply to our homes • Voltage of 230 v a.c.

  6. Plugs and electrical cable An electrical plug is inserted into a socket and the cable which is attached to the plug carries electricity to the appliance.

  7. Inside an electrical cable copper There are three wires made out of copper Each wire is surrounded in plastic. insulating plastic

  8. Materials in a plug

  9. The live wire carries a current from the mains supply to the applicance . It is brown • The earth wire is a safety device that allows current to flow from the appliance to the plug if there is a fault in the appliance. It is green and yellow! The neutral wire carries the current from the appliance to the mains supply. It is blue

  10. What is a fuse? A fuse is a safety device

  11. When a large current flows the wire becomes hot. If too much current flows, the wire overheats and melts which breaks the circuit. How does a fuse work? terminals case made of insulating material thin wire with high resistance

  12. How to wire a plug correctly • Open the plug • Connect live wire to the live pin with the fuse on it • Connect the neutral wire to the neutral pin • Connect theearth wireto the earth pin! • Close the plug!

  13. Plugs – true or false?

  14. Power ratings • Power is the amount of energy used per unit time. • Power is measured in watts.

  15. High power rating • Things that use a lot of power e.g electric heater, dishwasher

  16. Low power rating • Appliances that use a small amount of power E.g CD player 15 W power rating, computer 70 W

  17. Paying for electricity in Ireland? • It depends on how many units of energy used • Unit of energy used = kilowatt hour. • A kilowatt hour = amount of energy needed for 1kW of power to be used for 1 hour.

  18. cost = number of kilowatts x number of hours x cost per hour Cost of electricity

  19. Buying electricity problem A kettle has a power rating of 8 kW It is turned on for 5 hours. If electricity costs 10c per kilowatt hour how much does it cost to use the kettle? Cost of electricity: cost = number of kW x number of hrs x cost per hr = 8kW x 5hrs x 10c/kWhr = 400c or 4 euro

  20. A toaster has a power rating of 6 kW It is turned on for 3 hours. If electricity costs 9 c per kilowatt hour how much does it cost to use the kettle? Cost of electricity: cost = number of kW x number of hrs x cost per hr = 6kW x 3hrs x 9c/kWhr = 162c or 1 euro 62 cent

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