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Science 10

Science 10. Aim: What is energy. Agenda. Science Sizzler. Energy Notes Cont. Lunch Next class. Evidence of Energy Conversion Motion - Ex: baseball pitcher Change in Position (gravitational potential energy) - Ex: lifting a book Change in Shape - Ex: elastic bands

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Science 10

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  1. Science 10 • Aim: What is energy

  2. Agenda • Science Sizzler. • Energy Notes Cont. • Lunch • Next class

  3. Evidence of Energy Conversion • Motion • - Ex: baseball pitcher • Change in Position (gravitational potential energy) • - Ex: lifting a book • Change in Shape • - Ex: elastic bands • Change in Temperature • - Ex: cooking Energy Conversions -Energy changing from one form to another

  4. Kinetic Vs. Potential Energy • Potential Energy (PE) - Stored energy that can converted into other forms • Kinetic Energy (KE) - Energy due to motion

  5. Can Energy Disappear??

  6. Law of Conservation of Energy • Energy Cannot be created or destroyed, only converted from one form to another • Energy at the beginning of a system, input energy = output energy

  7. Energy inNature & Technology

  8. The Law of Conservation of Energy 1) energymay neither be created nor destroyed. 2) the total amount of energy in a system remains constant over time

  9. Energy Transfer Technologies • Hydro-electric Dams • Coal-Burning Power Stations • Nuclear Power • Radiation • Solar Cells • Fuel Cells

  10. Hydro-electric Dams

  11. Coal-burning Power Station

  12. Nuclear Energy Conversions • CANDU Reactor = use the splitting of an atom (fission) to fuel the reactor and make electricity http://www.youtube.com/watch?v=jNOzh4Kwgpw (CANDU = CANada Deuterium-Uranium reactor)

  13. Radiation as an Energy Source Radiation (electromagnetic waves or as moving subatomic particles)  thermal energy  heats water  steam turns turbine  creates mechanical energy that goes into a generator  creates electrical energy

  14. Solar Cells • composed of 2 layers of silicon (one with phosphorus, one with boron) • When light hits the layers, it causes electrons to break free from the silicon • phosphorus layer = becomes negative • boron layer = becomes positive • Poles are created and electricity is made (flowing of electrons)

  15. Fuel Cells - Convert chemical energy in hydrogen into electrical energy - Does not need recharging – needs fuel (water & heat) to work - Is popular in spacecrafts Hydrogen fuel cells operate like a battery

  16. The Development of Steam Engines A steam engineis … ….any machine that generates steam and converts the steam pressure into mechanical motion.

  17. The First “Steam Engine” • Hero of Alexandria (Greek inventor) invented the first “steam engine” sometime between 130 B.C. and 70 A.D. • It was really only a toy, since it didn’t have any practical purpose.

  18. The First Practical Steam Engine… • Were developed in the 1600’s. • Designed to remove water from coal mines.

  19. The Savery Steam Engine • Thomas Savery of England built the first practical machine to pump water from coalmines. • Patented in 1698. • Very inefficient and costly to operate. • Relied on atmospheric pressure to push the water out of the mine.

  20. The Newcomen Steam Engine • Designed an atmospheric engine in 1712. • Big improvement from Savery’sengine. - Didn’t have to open valves manually. • Used atmospheric pressure to push the piston down • Also used atmospheric pressure to pump water out of mines. • Engine wore out quickly due to constant heating and cooling of parts.

  21. The ‘Double Acting’ Steam Engine • Invented by James Wattin 1796 • Was the model for all steam engines for years to come.

  22. The ‘Double Acting’ Steam Engine • Steam condensed by a spray of water in a separate chamber. This caused engine parts to always be hot, so they lasted longer. • Designed a system of gears and levers so the piston could turn a wheel. This provided power for many industries.

  23. Steam engines and the Industrial Revolution • Watt’s steam engine was responsible for the rapid development of the Industrial Revolution, which began in the late 1700’s. • Powered machines in flourmills, saw mills, and textile factories.

  24. Steam powered tractors were used to produce food for the growing populations. • Steam powered locomotives and paddle-wheel steamboats were developed to transport people and supplies

  25. Steam TurbinesDesigned in 1884 • Steam-Turbine Engines are used to power giant ocean liners and cruise ships. • Steam turbine engines do not use pistons; they use curved blades similar to fan blades. • Modern turbines use several rotors and several sets of stationary blades.

  26. Theories of Heat

  27. What is heat??

  28. Early Theories of Heat Theory of the 4 Elements Approx. 450 BC • All matter consists of some combination of earth, air, fire, and water • Many objects contain fire, and when they burn fire is released

  29. Early Theories of Heat PhlogistonTheory Early 1700s  Substances that burn contain an invisible liquid called Phlogiston that flows out when burned

  30. Early Theories of Heat Caloric Theory Late 1700s  Caloric (heat) is a mass-less substances found in all substances  Caloric flows from warmer to cooler objects  1 Calorie = amount of Caloric needed to increase the temperature of 1 g of water 1oC

  31. Modern Theories of Heat

  32. Count Rumford’s Hypothesis 1780s • While making a cannon, the tools and metal became very hot. This didn’t make sense with the Caloric Theory • Rumford suggested ‘caloric’ (the mass-less substance) did not exist and that the mechanical energy being exerted on the cannon and tools was being converted to heat

  33. Julius Mayer’s Hypothesis 1840s • Doctor • Suggested heat was related to energy • Proposed that energy from food was used to do physical work and to heat the body • Because he wasn’t schooled in math/physics, his ideas weren’t accepted • Despite his work, James Joule was given credit for discovering the mechanical equivalent of heat

  34. James Joule Late 1800s Conducted numerous experiments to determine the mechanical equivalent of heat • Measured the force that gravity exerts on the weight and the distance the weight fell  From this he determined the work done on the water and related it to temperature

  35. The Kinetic-Molecular Theory • The molecules of a substance are in constant, random motion. The faster they move, the warmer the substance gets

  36. Energy and Work Work = The Transfer of Mechanical Energy from One Object to Another Work: Is done when a force is applied over a distance  W = F x Δd Joule (J) Newton (N) Distance (m) Force = A Push or Pull on an Object

  37. You exert a force of 25 N on your textbook while lifting it a height of 1.4 m to put it on the shelf. How much work did you do on the textbook? • If you push on a wall as hard as you can and it does not move, do you do any work on it?

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