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# Energy and Efficiency

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• 1. WHEN G.P.E. IS CONVERTED ENTIRELY TO K.E. OR VICE VERSA...  Ek = ½mv2  Ep = mgh  By Principle of Conservation of Energy, Ek = Ep ½mv2 = mgh ½v2 = gh v = 2gh
• 2. 2 Principle of Conservation of Energy and the non-ideal pendulum 1. Lost in EP  Gain in EK + Thermal energy (friction) 2. Lost in EK  Gain in EP + Thermal energy (friction) Height gained is lower than the original because some of the energy has been converted to thermal energy. (1) (2) The pendulum eventually comes to a stop. Video - Ballistic pendulum
• 3. EFFICIENCY What does efficiency refer to?
• 4. EFFICIENCY  Recall Senoko Power Station:  Note the conversion of energy from one form to another
• 5. EFFICIENCY  Do you agree? The chemical energy of the fuel is fully converted to electrical energy because the Principle of Conservation of Energy states that energy cannot be created nor destroyed.
• 6. EFFICIENCY  Some of the energy is converted to heat, light and sound. The energy conversion is thus not 100% Wouldn’t this violate the Principle of Conservation of Energy?
• 7. EFFICIENCY No, because the total sum of heat, light, sound and electrical energy is equal to the chemical energy of the fuel
• 8. LIGHT BULB
• 9. EFFICIENCY  In a system, the ratio of useful energy output to the total energy input is known as the efficiency of the system.  Efficiency is expressed as a percentage
• 10. EFFICIENCY  Calculate the efficiency of the light bulb.