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KS4 Physics

KS4 Physics. Energy Transfers. Contents. Energy Transfers. Useful energy. Conservation of energy. Wasted energy. Efficiency. Summary activities. Useful energy transfer. Many everyday objects are designed to transfer energy from one form into another useful form.

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KS4 Physics

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  1. KS4 Physics Energy Transfers

  2. Contents Energy Transfers Useful energy Conservation of energy Wasted energy Efficiency Summary activities

  3. Useful energy transfer Many everyday objects are designed to transfer energy from one form into another useful form. What energy transfer is an electric fan designed to carry out? electrical energy kinetic energy

  4. What is the useful energy transfer? What energy transfer is a speaker designed to carry out? electrical energy sound energy

  5. What is the useful energy transfer? What energy transfer is a wind farm designed to carry out? electrical energy kinetic energy

  6. What is the useful energy transfer? What energy transfer is a hydroelectric power station designed to carry out? gravitational energy electrical energy

  7. Useful energy transfers Complete the input and useful output energies for the devices in this table. heat electrical electrical light kinetic elastic heat chemical

  8. Contents Energy Transfers Usefulenergy Conservation of energy Wasted energy Efficiency Summary activities

  9. Law of conservation of energy Allenergytransfersfollowthelawofconservationofenergy: Energy cannot be created or destroyed, just changed in form. • This means that energy never just ‘disappears’. • The total amount of energy always stays the same, i.e. the total input energy = total output energy. • In most energy transfers, the energy is transferred to several different forms, which may be useful or not useful. • The energy that is transferred to unwanted forms of energy is wasted.

  10. Energy transfer in a television An energy transfer diagram shows the input energy and the output energies for a device. This includes all the useful and wasted forms of energy. For example, in a television: light electrical sound heat

  11. Energy transfer in a radio What are the main energy transfers in a radio? (Don’t forget the wasted energy.) sound electrical heat

  12. Energy transfer in a car engine What are the main energy transfers in a car engine? (Don’t forget the wasted energy.) kinetic chemical sound heat

  13. Identifying energy transfers

  14. Falling objects When an object falls in a gravitational field: Gravitational potential energy (GPE) at the top equals the kinetic energy (KE) of the object just before it hits the ground. If a diver has 4000J of GPE at the top of a cliff, how much KE will she have just before she hits the sea? _________ 4000J Assuming no energy is lost by air resistance!!!

  15. Gerald the Human Cannonball

  16. Contents Energy Transfers Useful energy Conservation of energy Wasted energy Efficiency Summary activities

  17. Wasted energy Whenever energy is changed from one form to another, some energy is alwayswasted. • Energy is usually wasted as: • heat energy; • sound energy. • All electrical devices produce a small amount of heat energy, which is normally wasted.

  18. Wasted sound energy car engine hairdryer jet engine If you can hear a device that is not designed to make noise then energy is wasted as sound. Examples of devices that waste energy as sound include: washing machine

  19. Wasted heat energy car engine television If a device gets warm and it is not designed to get warm then energy is wasted as heat. Examples of devices that waste energy as heat include: mobile phone charger radio

  20. Which type of energy is wasted?

  21. What happens to wasted energy? What happens to the wasted energy produced whenever energy is changed from one form to another? (Remember that energy cannot be created or destroyed.) Wasted energy spreads out into the surroundings – this is called dissipated energy. This dissipated energy is too spread out to do useful work and so cannot be re-used. This is why it is important to reduce the amount of energy that is wasted.

  22. Contents Energy Transfers Useful energy Conservation of energy Wastedenergy Efficiency Summary activities

  23. 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. Energy efficient light bulbs are more efficient than normal light bulbs because they w____ less energy. More of the e_______ energy that they are supplied with is converted into l____ energy and not h___. aste lectrical ight eat

  24. Calculating efficiency useful energy out total energy in efficiency = The efficiency of a device can be calculated using this formula: Useful energy is measured in joules (J). Total energy is measured in joules (J). This means that efficiency does not have any units. It is a number between 0 and 1 or a percentage.

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

  26. 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 heat Efficiency = Useful Total = 96 J 300J = 0.32 or 32% 0.32 or 32%

  27. Efficiency of a television This television converts 2 000J 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

  28. Efficiency questions

  29. Contents Energy Transfers Useful energy Conservation of energy Wastedenergy Efficiency Summary activities

  30. Glossary • dissipated – Energy that spreads out into its surroundings so that it is no longer useful. • efficiency – A measure of how good a device is at changing energy from one form to another. • energy transfer – The process of changing energy from one form into another. • input energy – The energy going into a device. • output energy – The forms of energy produced by a device. • useful energy– Energy in a form that is wanted. • wasted energy –Energy in a form that is not wanted or is not used.

  31. Anagrams

  32. Energy transfers – summary

  33. Multiple-choice quiz

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