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# Physics presentation 1.3

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by

## Jess Slater

on 20 December 2012

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#### Transcript of Physics presentation 1.3

The usefulness of electric devices Physics 1.3 Cost of Electricity Electrical appliances convert electrical energy into other forms of energy used the home. Home owners with then receive a bill for this energy every three months, which contains the cost of the energy they have used. Energy transformations. Energy is transferred into another form all the time when an electrical device is in use. The energy in our homes is commonly transformed into light, sound or kinetic energy through household appliances.
Energy is wasted a lot because as it is being used, it is using it's energy to also do something else that is not needed or required. For example a light bulb's purpose is to give out light, but it also gives out heat. This heat energy is then wasted. Light bulbs can give different brightnesses of light depending on their power waiting. Costing The unit used to charge customers for electricity in the kilowatt hour. (kWh) = Number of energy units
used (kWh). Kilowatt hours
x Time in hours The Equation... An electricity bill Power Power measures how quickly energy can be transferred. It is calculated by dividing the energy transferred by the time taken to transfer the energy. The unit in which power is measured is the Watts (W). Power (W) Energy transferred (J) Time taken to transfer energy (s) Rearranging Equations x E P t Energy and work Energy, including electricity, is measured in Joules (J). All electrical devices transfer electrical energy into other forms of energy. For example, a light bulb transfers electricity into light and heat When a device transfers energy, we say that it does work for us. The amount of work done is the same as the amount of energy transferred. Light energy Heat energy Electricity Sankey diagram Example Question What relationship does the graph show? 1 As the temperature setting increases, the power increases.

2 As the temperature setting increases, the power decreases.

3 As the temperature setting decreases, the power increases.

4 There is no relationship. 2.5 2.0 1.5 1.0 0.5 0 0 20 40 60 80 100 Power in
kilowatts
(KW) Temperature Setting in *C By Jess Slater, Cameron Harrison, Charlotte Smith, Alicia MacRae and Chloe Quick Energy and work Energy, including electricity, is measured in j _ _ _ _ _ (J). All electrical devices transfer energy into other forms of energy. For example, a light bulb transfers electricity into l _ _ _ _ _ and h _ _ _ energy. When a device transfers energy, we say that it does w _ _ _ for us. The amount of work done is the same as the amount of energy transferred. Answer: joules, light, heat, work Answer- 1
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