Using Energy

Using Energy

1. Forms of Energy

   • Chemical Energy (fuel including food and is released during chemical reactions
   • Kinetic Energy
   • Gravitational potential Energy (due to position)
   • Elastic Potential Energy( energy through strain and stretch)
   • Thermal Energy
   • Electrical Energy
   • Light Energy
   • Sound Energy
   • Dropping an object: Gravitational energy at the top, turns to Kinetic when hits the floor then Heat and Sound energy

2. Conservation of Energy

   • means that no energy is created or destroyed
     • I.E : Total Energy before transfer = total energy after transfer
     • energy supplied = useful energy +wasted energy

3. Useful Energy and Wasted Energy

   • useful energy is energy transferred to where it is wanted in the form it is wanted!
   • wasted energy is energy not usefully transfered
     • Wasted energy is dissipated (spread out) to surrroundings
       • Useful energy eventually transfers to the surroundings too
         • the more energy is spread out the less useful it is
           • it is hard to get back energy and gases in the surroundings therefore not useful
         • useful energy for wheels of car is transferred to energy heating tyres and that energy is transfered to the actual road
       • heat is spread out of the tv

4. Energy and Efficiency

   • Weight is measured in Newtons (n) ( 1 kilogram on Earth = 10N)
   • Energy is measured in Joules (J) energy needed to lift 1N by 1 metre is 1joule
   • Efficiency = (useful energy transferred / total energy supplied) x 100
     • Examples
       • Lightbulb = for every 100J of energy 5J of energy is transferred to light..
         • efficiency = 5/100 x100
           • 5% efficient
       • energy needed to carry two skiers to top of mountian by chairlift is 240000J
         • motor is 40% efficient
           • calculate wasted energy
             • 0.4 = useful energy/ total energy
               • 0.4 = 240 000 / x
                 • 0.4x= 240 000
                   • x= 240 000/ 0.4
                     • total energy imput = 600 000
                       • 600 000 - 240 000 = wasted energy output
                         • = 360 000