energy

energy

energy transfer
1. energy is never used up. instead its just transferred between different energy stores and different objects
2. energy is transferred between stores.
  1. thermal
  2. kinetic
  3. gravitational potential
  4. elastic potential
  5. chemical
  6. magnetic
  7. nucleur
3. when a system (a single object) changes, energy is transferred
4. energy can be transferred by heating
  1. or doing work......
    1. work done is just another way of saying energy transferred
      1. work can be done when current flows (work is done against resistance in a circuit) or by a force moving an object.
kinetic and potential energy stores
1. movement means energy in an objects kinetic energy store
  1. anything thats moving has energy in its kinetic energy store
    1. energy is transferred TO this store when an object speeds up and is transferred AWAY from this store when am object slows down
2. Ek = 1/2 x m x v squared
3. raised objects store energy in gravitational potential energy stores
  1. lifting an object in a gravitational field requires work. this causes transfer of energy to the gravitational potential enerygy
4. Ep (gpe) = mgh
5. falling objects also transfer energy
  1. when something falls energy from its gravitational potential energy store is transferred to its kinetic energy store
  2. for a falling object when there is no air resistance......
    1. energy lost from the gpe store = energy gained in the kinetic energy store
6. stretching or squashing an object can transfer energy to its elastic potential energy store
  1. Ee = 1/2 x k x e squared
SHC
1. heres the equation that links energy transferred to specific heat capacity......
  1. change in E = M x C (shc) x temp change
conservation of energy and power
1. energy is NEVER destroyed
2. energy can be transferred usefully, stored or dissipated , but can never be destroyed.
3. when energy is transferred between stores, not all of the energy is transferred usefully into the store that you want it to go in
4. dissipated energy is sometimes called 'wasted energy' because the energy is being stored in a way that is not useful
conduction and convection
1. when an object is heated , energy is transferred to the kinetic energy stores of its particles.
  1. this causes the particles to vibrate more and to collide with each other. during these collisions, energy is transferred between the particles kinetic energy stores. this is conduction.
2. because liquids and gases can flow, the warmer and less dense region will rise above denser, cooler regions. so energetic particles move away from hotter to cooler regions. this is convection.
insulation
1. thick walls
  1. made from a material with a low thermal conductivity.
2. cavity walls
3. draught excluders
4. double glazed windows
efficiency
1. useful output energy transfer // total input energy transfer
  1. OR ....
    1. useful power output // total power input

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	Created by Flora Greening over 7 years ago