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- 1. Paying for electricity <ul><li>By the end of the lesson I will know; </li></ul><ul><li>how to calculate energy use in kWh </li></ul><ul><li>How to calculate cost </li></ul>Starter try to finish off the worksheet from last lesson working out power of the appliance, remember power = energy (in joules)/ time (second)
- 2. kWh = kW x hr Cost = kWh x cost of 1 unit
- 3. Device Power (in kW) Time of use (in hours) Energy transferred (in kW h) Computer 0.4 3.0 Heater 2.0 2.0 Kettle 3.0 0.2 Lamp 0.1 5.0 Microwave oven 1.0 2 0.2 Television 0.2 2.0
- 4. Device Power (in kW) Time of use (in hours) Energy transferred (in kW h) Computer 0.4 3.0 1.2 Heater 2.0 2.0 Kettle 3.0 0.2 Lamp 0.1 5.0 Microwave oven 1.0 2 0.2 Television 0.2 2.0
- 5. Device Power (in kW) Time of use (in hours) Energy transferred (in kW h) Computer 0.4 3.0 1.2 Heater 2.0 2.0 4.0 Kettle 3.0 0.2 Lamp 0.1 5.0 Microwave oven 1.0 2 0.2 Television 0.2 2.0
- 6. Device Power (in kW) Time of use (in hours) Energy transferred (in kW h) Computer 0.4 3.0 1.2 Heater 2.0 2.0 4.0 Kettle 3.0 0.2 0.6 Lamp 0.1 5.0 Microwave oven 1.0 2 0.2 Television 0.2 2.0
- 7. Device Power (in kW) Time of use (in hours) Energy transferred (in kW h) Computer 0.4 3.0 1.2 Heater 2.0 2.0 4.0 Kettle 3.0 0.2 0.6 Lamp 0.1 5.0 0.5 Microwave oven 1.0 2 0.2 Television 0.2 2.0
- 8. Device Power (in kW) Time of use (in hours) Energy transferred (in kW h) Computer 0.4 3.0 1.2 Heater 2.0 2.0 4.0 Kettle 3.0 0.2 0.6 Lamp 0.1 5.0 0.5 Microwave oven 1.0 2 0.2 0.4 Television 0.2 2.0
- 9. Device Power (in kW) Time of use (in hours) Energy transferred (in kW h) Computer 0.4 3.0 1.2 Heater 2.0 2.0 4.0 Kettle 3.0 0.2 0.6 Lamp 0.1 5.0 0.5 Microwave oven 1.0 2 0.2 0.4 Television 0.2 2.0 0.4
- 10. Total energy = 1.2+4.0+0.6+0.5+0.4+0.4 = 7.1 kWh
- 11. Total cost = 7.1 KWh X 7 p/kWh = 49.7 p
- 12. a) Calculate the energy transferred, in kW h, when: i) A 1200 W microwave oven is used for 20 minutes. ii) A 2.0 kW electric heater is used for two hours. iii) A 0.6 kW hairdryer is used for 30 minutes.
- 13. a) Calculate the energy transferred, in kW h, when: i) A 1200 W microwave oven is used for 20 minutes. 1.2 kW x 1/3 h = 0.4 kWh ii) A 2.0 kW electric heater is used for two hours. iii) A 0.6 kW hairdryer is used for 30 minutes.
- 14. a) Calculate the energy transferred, in kW h, when: i) A 1200 W microwave oven is used for 20 minutes. 1.2 kW x 1/3 h = 0.4 kWh ii) A 2.0 kW electric heater is used for two hours. 2 kW x 2h = 4 kWh iii) A 0.6 kW hairdryer is used for 30 minutes.
- 15. <ul><li>a) Calculate the energy transferred, in kW h, when: </li></ul><ul><li>i) A 1200 W microwave oven is used for 20 minutes. </li></ul><ul><li>1.2 kW x 1/3 h = 0.4 kWh </li></ul><ul><li>ii) A 2.0 kW electric heater is used for two hours. </li></ul><ul><li>2 kW x 2h = 4 kWh </li></ul><ul><li>A 0.6 kW hairdryer is used for 30 minutes. </li></ul><ul><li>0.6 kW X o.5 h = 0.3 kWh </li></ul>
- 16. <ul><li>a) Calculate the energy transferred, in kW h, when: </li></ul><ul><li>i) A 1200 W microwave oven is used for 20 minutes. </li></ul><ul><li>1.2 kW x 1/3 h = 0.4 kWh </li></ul><ul><li>ii) A 2.0 kW electric heater is used for two hours. </li></ul><ul><li>2 kW x 2h = 4 kWh </li></ul><ul><li>A 0.6 kW hairdryer is used for 30 minutes. </li></ul><ul><li>0.6 kW X o.5 h = 0.3 kWh </li></ul>b)i)Calculate the total energy transferred in a). ii)Calculate the cost of the electricity used in a) if each kW h of energy transferred costs 8 p.
- 17. <ul><li>a) Calculate the energy transferred, in kW h, when: </li></ul><ul><li>i) A 1200 W microwave oven is used for 20 minutes. </li></ul><ul><li>1.2 kW x 1/3 h = 0.4 kWh </li></ul><ul><li>ii) A 2.0 kW electric heater is used for two hours. </li></ul><ul><li>2 kW x 2h = 4 kWh </li></ul><ul><li>A 0.6 kW hairdryer is used for 30 minutes. </li></ul><ul><li>0.6 kW X o.5 h = 0.3 kWh </li></ul>b)i)Calculate the total energy transferred in a). = 0.4 + 4 + 0.3 = 4.7 kWh ii)Calculate the cost of the electricity used in a) if each kW h of energy transferred costs 8 p.
- 18. <ul><li>a) Calculate the energy transferred, in kW h, when: </li></ul><ul><li>i) A 1200 W microwave oven is used for 20 minutes. </li></ul><ul><li>1.2 kW x 1/3 h = 0.4 kWh </li></ul><ul><li>ii) A 2.0 kW electric heater is used for two hours. </li></ul><ul><li>2 kW x 2h = 4 kWh </li></ul><ul><li>A 0.6 kW hairdryer is used for 30 minutes. </li></ul><ul><li>0.6 kW X o.5 h = 0.3 kWh </li></ul>b)i)Calculate the total energy transferred in a). = 0.4 + 4 + 0.3 = 4.7 kWh ii)Calculate the cost of the electricity used in a) if each kW h of energy transferred costs 8 p. Total cost = 4.7 X 8 = 37.6p

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