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What is energy efficiency?

What is energy efficiency?. Efficiency is a measure of how good a device is at changing energy from one form to another. All devices waste energy, so the efficiency of a device is never 100%. The more efficient a device is the less energy is wasted.

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What is energy efficiency?

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  1. What is energy efficiency? Efficiency is a measure of how good a device is at changing energy from one form to another. All devices waste energy, so the efficiency of a device is never 100%. The more efficient a device is the less energy is wasted. An energy-efficient light bulb is more efficient than a filament bulb because it wastes less energy. It converts a greater proportion of the energy that it is supplied with into light energy and not heat.

  2. Why is energy efficiency important? New electrical appliances display information about how energy efficient they are. This helps consumers to identify which appliance will use the least energy and cost the least to run. Energy efficiency is not just about saving money, it’s also about saving the planet. Appliances that are more efficient need less electricity, and so less fossil fuel needs to be burnt in fossil-fuel power stations. This is important for reducing pollution and the effects of climate change.

  3. How is energy efficiency calculated? The energy efficiency of a device can be calculated using this formula: useful output energy total input energy energy efficiency = • Useful energy is measured in joules (J). • Total energy is measured in joules (J). • Energy efficiency does not have any units. • It is a number between 0 and 1 which can be converted into a percentage by multiplying by 100.

  4. Calculate the efficiency of a bulb This filament bulb is supplied with 100J of electrical energy, which it converts to 45J of light energy. • How much energy • is wasted? • In what form is the energy wasted? • What is the efficiency • of the bulb? Wasted energy = Total – Useful = 100J – 45J = 55J 55J Efficiency= Useful Total = 45 J 100 J = 0.45 or 45% heat 0.45 or 45%

  5. Calculate the efficiency of a radio This radio is supplied with 300J of electrical energy which it converts to 96J of sound energy. Wasted energy = Total – Useful = 300J – 96J = 204J • How much energy • is wasted? • In what form is the energy wasted? • What is the efficiency of the radio? 204J Efficiency = Useful Total = 96 J 300J = 0.32 or 32% heat 0.32 or 32%

  6. Calculate the efficiency of a television This television converts 2000J of electrical energy into useful energy at an efficiency of 65%. • What useful energy does a television produce? • How much useful • energy is produced? light and sound Efficiency = Useful Total Useful = Efficiency x Total = 0.65 x 2000J = 1300J 1300J

  7. Energy efficiency calculations – activity

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