# GCSE Physics

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The flashcards below were created by user ghoran on FreezingBlue Flashcards.

1. Mr Macintosh wants to work out how much energy he could save if he turned all his electrical appliances off overnight , instead of leaving them on standby .
On Tuesday night , he leaves all his appliances on standby . He takes a meter reading at 9pm before going to bed and at 9am the next morning when he wakes up
On thrusday night he repeats the experiment , but this time he turns off all his appliances .
tuesday reading at 9pm : 13592.42 kWh
wednesday reading at 9am : 13598.63 kWh
thursday reading at 9pm : 13646.68 kWh
friday reading at 9am : 13649.41 kWh
calculate the amount of energy Mr Macintosh saved by turning off his electrical aplliances overnigjt , rather than leaving them on standby
• differences between readings on first night
• 13598.63-13592.42 = 6.21kWh
• differences between readings on second night
• 13649.41-13646.68 = 2.73kWh
• difference between energy used on first night and second night
• 6.21-2.73 = 3.48 kWh
2. a mains powered drill has a power output of 1.2kW
a battery powered drill has a power output of 200W and a battery life of 8 hours
suggest two reasons why someone might choose to buy the baterry powered drill rather than the mains powered drill
• it can be used in areas where there is no acess to mains electricity
• it's easier to use as there is no power cord in the way
• it uses less energy
3. a battery powered lamp takes six hours to charge fully when connected to a 400 W poer suplly . This gives the lamp enough energy for 8 hours of use . A mains powered lamp has a power rating of 1.6 kW
if both lamps are used for 8 hours
A) calculate the difference in the amount of energy used . Give your answer in kWh
B) if the cost of electricity is 12p per kWh , calculate the difference in cost for using both lamps for 8 hours
C) suggest why somebody on a camping trip may choose to buy a wind up lamp ionstead of the mains powered or battery powered lamps required above
• energy = power * time
• cost = number of kWh used and price per kWh
• a) 0.4*6 = 204 kWh
• 1.6*8 = 12.8 kWh
• difference = 12.8-2.4 = 10.4kWh
• b) 12 * 10.4 = 124.8p
• c) becuase there might not be a an electricity supply where they are camping , so they will not be able to use a main powered lamp or recharge the battery powered lamp when it runs out . the wind up lamp doesn't require any electricity to re-charge
4. acess to electricity can improve people's standard of living in developing countires . give two examples of how electricity can help improve public health in developing countires
it can be used to power : x-ray machines , refrigeration of medicines or vacines , equipment for operations , refrigeration of food

### Card Set Information

 Author: ghoran ID: 147413 Filename: GCSE Physics Updated: 2012-04-13 10:03:55 Tags: usefulness electrical devices Folders: Description: part three Show Answers:

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