energy

• a system is an object or a group of objects

  when it changes, energy is transferred
• 5 energy stores:

  • kinetic - energy gained by moving quicker
  • gravitational potential - energy gained by lifting an object higher
  • thermal - energy gained by heating it up
  • chemical - energy gained due to a chemical reaction
  • elastic potential - energy gained when an object is stretched or squashed
• 4 energy pathways:

  • electrical
  • mechanical
  • radiation (by light or sound)
  • heating
• • work done is another way of saying energy transferred
  • work can be done when a current flows or by a force acting on an object
• conservation of energy:

  energy is not created or destroyed, it is transferred between stores or dissipated into the surroundings
• power is the rate at which energy is transferred or the rate at which work is done
• conduction :

  • occurs in solids
  • energy transferred by heating to thermal store of object, shared to kinetic store of particles which vibrate more and collide with others causing energy to be transferred between particles
  • higher the thermal conductivity, the higher the rate of energy transferred across the material
  • the thicker the walls, the higher the thermal conductivity, the slower a building will lose heat
• renewable energy:

  • energy that can be replenished as quickly as it is used
  • solar, wind, tidal, wave, hydroelectric, geothermal, biogas
  • unreliable as it wont always be sunny/windy
  • expensive
  • ruins landscapes
  • destroys habitats
• non-renewable:

  • energy that cannot be replenished as quickly as it is used
  • nuclear, oil, coal, gas
  • reliable as it is always there
  • will run out
  • contributes to climate change as greenhouse gases are released
• uses of energy:

  transport, electricity generation, heating