7.5 electrical energy and power

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SPM Malaysia Physics Syllabus Chapter 7: Electricity Part 5: Electrical Energy and Power

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7.5 electrical energy and power

  1. 1. Chapter 7: ElectricityElectrical Energy and Power
  2. 2. The ability of the electriccurrent to do work
  3. 3. Electrical Energy Supplied by a source of electricitySuch as a cell or battery When current flows in a closed circuit
  4. 4. Electrical Energy Converts into other forms such as: heat light mechanicalBy electrical appliances when current flows in it
  5. 5. Potential Difference, V Energy, E transferred by 1 C of charge, Q that moves between two points
  6. 6. CurrentRate of charge flow
  7. 7. Combining these two equations, we get
  8. 8. PowerUnit = Watt (W)
  9. 9. An Electric Kettle Marked 240 V 1500 W Means that the kettle consumes 1500 J of electrical energy every second its connected to 240 V
  10. 10. The larger the power rating,the more energy consumed in every second. The longer the usage time, the more electrical energy is consumed.
  11. 11. 1 kilowatt-hour (kWh) The amount of energy consumed by an electrical applianceIn 1 hour At the rate of 1 kilowatt
  12. 12. 1 kWh = 1 unit of energy1 kWh 3.6 x 106 J 1 kW x 1 hr 100 W x 3600 s
  13. 13. Efficiency Percentage of output power to the input power
  14. 14. The efficiency of an electrical appliance Is always less than 100%Because some energy is lostthe form of heat and sound
  15. 15. Energy EfficiencyUsing energy efficient devices to gain a higher level of useful outputs using less input
  16. 16. Increasing energy efficiency Reduces costs And also assisting in energy conservation
  17. 17. Energy efficient lightings Use compact fluorescent bulbs instead of regular incandescent bulbs
  18. 18. Utilize electrical appliances wiselyRun washingmachines onfull load only
  19. 19. Utilize electrical appliances wisely Iron clothes inbulk (i.e. severalpieces at a time)
  20. 20. Utilize electrical appliances wisely Limit usage or air conditioning and lighting Switch them off when you leave the room
  21. 21. Utilize electrical appliances wiselyClean air filters in air conditioners and clothes dryers regularly
  22. 22. Utilize electrical appliances wiselyDefrost refrigerators regularly – so that your freezer don’t work so hard
  23. 23. Utilize electrical appliances wisely Improve ventilation and air flow Better ventilation reduces cooling load of air conditioners
  24. 24. A fuse – a short piece of thin wireWhich overheats when current above a certain value flows through it
  25. 25. The fuse melts when a current that is too high flows during a short circuitThis prevents overheating of the wire which would cause a fire
  26. 26. If power rating of an appliance is960 W and 240 V, then normal current = 4 A Fuse to be used must be of higher current:- so use 5 A fuse
  27. 27. Earth Wire, E Three Pin Plug (green) Safety wire – connects appliance to earth Live Wire, L (brown)Neutral Wire, Current flows N (blue) through circuitZero Potential Difference
  28. 28. Three Pin Plug If a Live Wire touches the metal body of the appliance, a large current would immediately flow to the earth and breaks the fuse. This will avoid someone from being electrocuted.
  29. 29. Pic credits• Flickr / Plug Face - Day 3/365 / Jake Mates • Flickr / 148:365 - 09/25/2012 - Blown Fuse / Shardayy• Flickr / Plasma 5/ limowreck666 • Flickr / Con – Fused / canonsnapper• Flickr / Pedagaggi Wind Turbines / Sebastiano • Flickr / Wiring a Plug / tjmwatson Pitruzzello• Flickr / Dying moments / limowreck666• Flickr / defying murphy’s law / vakas• Flickr / Vintage Blackboard / pareerica• Flickr / Ultraman + Mt. Fuji = JAPAN / emrank• Flickr / kettle / butkaj.com• Flickr / March of the washer-dryers / Worldislandinfo.com• Flickr / 3D Green Energy / StockMonkeys.Com• Flickr / Electric Fuel Cap - RAC Future Car Challenge / Dominic Alves• Flickr / Fluorescent Tube / jeancliclac• Flickr / 154/366 / hannah8ball• Flickr / untitled / John Steven Fernandez• Flickr / kitty TV / kassandrapoised• Flickr / Universal Iron and Drapery / firexbrat• Flickr / Only in Egypt / mnadi• Flickr / This means you!! / passiveaggressivenotes• Flickr / thefreezerstaresatme / expressionposthumus• Flickr / cityswing / i_gallagher• Flickr / made in england / fishyfish_arcade

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