Energy Conversion & Conservation Kim Lachler Updated 2015 NCES: 6.P.1

Energy Conversion the change from one form of energy to another

Energy Conversion Chemical energy We get our energy from chemical energy How_Our_Bodies_Use_Energy.mov How_Does_Food_Supply_Energy_.mov Remember plants get their energy from the sun; light energy By using photosynthesis they convert light energy into sugar- stored energy – potential energy We eat the plants or animals that eat the plants = potential energy for us We either store this energy- in fat – potential energy or use the energy to move – kinetic energy

Energy Conversion Calorie – how we measure the potential energy in food calorie = 4.2 Kilojoules

Energy Conversion A piece of buttered toast contains about 315 kilojoules of energy Jog for 6 minutes Bicycle for 10 minutes Walk briskly for 15 minutes Sleep for 1 ½ hours

Energy Conversion Machines can convert energy to make it into forms useful for us. Alarm clock – electrical energy  light and sound energy Battery – chemical energy  electrical energy Light bulb – electrical energy  light and thermal energy

Energy Conservation Any time energy is converted from one form to another, thermal energy is given off.

Energy Conservation Remember things move from potential energy to kinetic energy and back again. As this happens some of the energy is converted to thermal energy, so the potential energy becomes less and less.

Energy Conservation Energy is converted to thermal energy by friction Friction – a force that opposes motion between two surfaces that are in contact http://phet.colorado.edu/en/simulation/friction

Law of conservation of energy energy can not be created or destroyed but can be changed from one form to another

Law of conservation of energy Closed system Where you can measure all the different energies from start to finish of an action. The original potential energy = all the final energies mechanical energy ( potential + kinetic) sound energy thermal energy

Perpetual Motion Perpetual motion – a machine that would run forever without any additional energy No, because of friction. Is this possible?

Energy Efficient comparison of the amount of energy before a conversion with the amount of useful energy after a conversion. Some machines are not energy efficient – transferring most of the energy to a form you don’t want.

Energy Efficient Car engine convert only 25% of the gasoline to kinetic energy, the rest is converted to thermal energy as a result of friction.

Energy Efficient To help keep machines efficient oil aerodynamic

Bibliography Holt,Rinehart and Winsteon, North Carolina Holt Science & Technology, Holt,Rinehart and Winsteon, New York, 2005 Discovery Education, http://discoveryeducation.com, accessed 12/28/2010 What is a pendulum anyway?, http://www.calacademy.org/products/pendulum/page1.htm, accessed 12/28/2010