# Energy transfer, energy and efficiency, and the usefulness of electrical appliances

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• Created by: Victoria
• Created on: 04-06-13 19:30
Different materials at the same temperature can hold different amounts of energy.
E = M X C X feter (the O with the cross in the middle)
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Energy can be transformed and stored but not destroyed. Wasted energy heats its surroundings, eg- a light bulb, it creates light but it gets very hot.
Using a sankey diagram you can show this.
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The efficiency of a device refers to the amount of energy/power used. When energy is usefully transferred the greater the proportion of energy is usefully transferred and this is more cost effective.
if you replaced your old TV with a new one it will be more efficient even though it would cost more. But this could be a saving over the years, this is called pay back time. Efficiency=useful energy or power out/ by total energy or power in X 100%
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Most energy transferred into homes is electrical energy, its easily transferred by hairdryers-heat light energy-lamp sound-speakers kinetic energy, movement-electric fan
the amount of energy transferred depends on how long the appliance has been on and how fast the transfer of energy is. If we didn't have this reliable source of energy we would have power cuts so we would have to used another source of energy.
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Energy is measured in (J) joules, power gives the measure of the rate of the transfer. Power is measured in (W) watts or when bigger (KW) Kilowatts.
E = P X T
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## Other cards in this set

### Card 2

#### Front

Using a sankey diagram you can show this.

#### Back

Energy can be transformed and stored but not destroyed. Wasted energy heats its surroundings, eg- a light bulb, it creates light but it gets very hot.

### Card 3

#### Front

if you replaced your old TV with a new one it will be more efficient even though it would cost more. But this could be a saving over the years, this is called pay back time. Efficiency=useful energy or power out/ by total energy or power in X 100%

### Card 4

#### Front

the amount of energy transferred depends on how long the appliance has been on and how fast the transfer of energy is. If we didn't have this reliable source of energy we would have power cuts so we would have to used another source of energy.

E = P X T