Using energy

Using energy

1. Different forms of energy

   • Chemical energy = energy stored in fuel (including food), and is released when chemical reactions take place
     • Kinetic energy is the energy of a moving object
       • Gravitational potential energy (or GPE) is the energy of an object due to its position
         • Electrical energy is energy transferred by an electric current
           • Thermal (heat) energy is the energy of an object due to its temperature, partly because of the random kinetic energy of the particles of the object
             • Elastic (or strain) energy is the energy stored in a springy object when we squash or stretch it
               • Sound energy is energy created from sounds
     • Energy can only be transformed from one form to another
       • Energy cannot be lost it can ONLY be changed from 1 form to another
         • EXAMPLE= torch chemical energy in battery => electrical energy => light energy + thermal energy

2. Energy conservation

   • CONSERVATION OF ENERGY ! -- energy cannot be created or destroyed

3. Useful energy, Wasted energy ,Efficiency

   • Useful energy is energy transferred to where we want it to go
     • Wasted energy is energy which is not usefully transferred
       • Wasted energy spreads out to its surroundings.
         • EXAMPLE = the gears of a car get hot when the car is running, so thermal energy transfers from the gear box to the surrounding air
     • Useful energy eventually transfers to its surroundings too
       • EXAMPLE= , the useful energy supplied to the road wheels of a car changes into thermal energy of the tyres, the road and the surrounding air
   • Energy becomes less useful when its spread out
   • The Sankey diagram to the left shows how we can represent useful and wasted energy outputs from a machine or appliance
     • We can sum this up by using this general equation: energy supplied = useful energy delivered + energy wasted
       • For any device that transfers energy, we can use this to work out the energy efficiency of it:
         • useful energy transferred by __________________________________ device total energy supplied to device
           • Efficiency =