Physics Topic 6 - Energy and The Future

Physics Topic 6 - Energy and The Future

1. Energy Transfers

   • Thermal (heat energy), Light, Electrical, Kinetic (movement energy), Sound, Chemical Potential (such as the energy stored in batteries and fuels).
     • There are nine forms of energy.
       • Nuclear Potential (the energy stored in the nuclei of atoms), Gravitation Potential (the energy stored in things that can fall).
       • Elastic Potential (the energy stored by things that have been stretched or squashed and can spring back).
   • Energy can be moved from one place to another, this is called Energy Transfer. When this happens, energy often changes from one form to another.
   • Output Energy = Input Energy
   • Energy Conversion Diagrams (sometimes known as a Sankey Diagram).
     • This diagram shows the amount of energy converted or transferred. The width of the arrows represents the amount of energy in joules.

2. Efficiency

   • Efficiency means how good a device is at converting energy into useful forms is known as its efficiency.
   • useful energy transferred by the device ---------------------------------------------------- x 100% total energy supplied to the device
     • Efficiency =
   • Household goods are given an energy rating. Rather thatn give these as percentages, they are given as a colour coded grade from 'A' to 'G'.
     • With 'A' being the most efficient.

3. Heat Radiation

   • Some surfaces are better emitters of radiation that others.
   • A good absorber of heat is also a good emitter of heat.
   • Black is the best colour at absorbing thermal energy and black is also a good emitter.

4. The Earth's Temperature

   • The Earth's surface absorbs about half of the radiation that reaches the Earth and re-radiates the energy as infra-red radiation.
     • Which can heat up the atmosphere.
   • For the temperature of the Earth to stay the same, it must radiate energy into space at the same average rate as it absorbs it.
   • Too much greenhouse gas is bad for the atmosphere as it increases our carbon footprint.
     • But if all the greenhouse gases are removed from the atmosphere, the atmosphere will be able to hold less energy and it's temperature will decrease.