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Energy Sources and Transfer of Energy: Energy: Energy is defined as the ability (or capacity) to do work. Energy is measured in joules. When a body has 300 J of energy it means that it can do 300 J of work. It exists in different forms and when something happens, it is likely to be due to energy being transferred from one form to another. Energy transfer is needed to enable people, computers, machines and other devices to work and to enable processes and changes to occur. Different forms of energy: Type of energy Description Kinetic energy Gravitational potential energy Elastic potential energy Sound energy Internal energy Electrical potential energy Chemical potential energy Nuclear potential energy Type of energy Description The ability to do work due to the movement of a body The ability to do work due to the position of a body in a gravitational field The ability to do work due to the deformation of a body (e.g. a compressed or extended spring) The ability to do work due to the kinetic and potential energy of the vibrating particles in a sound wave The ability to do work due the random kinetic and potential energy of the particles in a body The ability to do work due to a the position of a charged particle in an electric field The ability to do work due to potential energy of the particles making up substances The ability to do work due to the potential energy of the subatomic particles in the nuclei of atoms Principle of the conservation of energy: The law of conservation of energy states that the total energy of a closed system is constant. For examination purposes, you should explain this statement by saying that this means that energy can be transformed from one form to another but it can neither be created nor destroyed β the total energy of a closed system will be the same before an interaction as after it. When energy is transformed from one form to another either: Work is done β for example, a man does work against gravity by lifting a large mass onto his shoulders. or Energy is radiated or received in the form of electromagnetic radiation β for example, internal energy is radiated away from the white hot filament of a lamp by infrared and light radiation. Kinetic Energy: Kinetic energy is the energy a body has because of its motion. For a body of mass m travelling with velocity v, πΎ. πΈ. = 1 ππ£ 2 2 WorkβKinetic Energy Theorem: When work is done on a system and the only change in the system is in its speed, the net work done on the system equals the change in kinetic energy of the system. Work done = change in kinetic energy Potential Energy: Potential energy is the energy a body has because of its position or condition / shape. Gravitational Potential Energy: Energy possessed by an object due to its position in a gravitational field is called gravitational potential energy. If mass of an object is m, and it is at a certain height h from ground, then G.P.E = mgh Elastic Potential Energy: When a force causes an object to change its shape, the particles of the body are either squashed together or pulled apart. Therefore, they have potential energy, called elastic potential energy. πΈπππ π‘ππ πππ‘πππ‘πππ πΈπππππ¦ = 1 2 ππ₯ 2 Conservation of Energy β Revisited: A mass m at height h above the ground has potential energy ο½ο mgh. When it falls, its velocity increases and it gains kinetic energy at the expense of its potential energy. If it starts from rest and air resistance is negligible, its kinetic energy on reaching the ground equals the potential energy lost by the mass. 1 ππ£ 2 = ππβ 2 Or loss of P.E. = gain in K.E. Renewable and non-renewable energy sources. The βusefulβ energy needs to be produced in controllable energy transfers. For example, in power stations a supply of useful energy in the form of electricity is produced. The βraw materialsβ for energy production are energy sources. These may be non-renewable or renewable. Apart from nuclear, geothermal, hydroelectric or tidal energy, the Sun is the source for all our energy resources. Renewable energy sources are not exhaustible. Their rate of generation is greater than rate of consumption. For example, wind energy, tidal energy. Non-renewable energy sources are exhaustible. Their rate of generation is less than their rate of consumption. For example, we consume fossil fuels more as compare to their rate of production. Energy Transfer: (1) chemical/fuel energy (a re-grouping of atoms), (2) hydroelectric generation (emphasising the mechanical energies involved), (3) solar energy (nuclei of atoms in the Sun), (4) nuclear energy, (5) geothermal energy, (6) wind energy. Nuclear fusion and fission in terms of energy-releasing processes: Electricity generation: Draw a block diagram of the process from fuel input to electricity output. Environmental issues associated with power generation. Work done by a force: Efficiency for an energy conversion: Efficiency of energy conversions in processes giving electrical output: Usefulness of energy output from a number of energy conversions: Power: Past Paper Questions: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36.