4. Energy

• Energy stores


  • Kinetic
  • Thermal
  • Chemical
  • Gravitational Potential
  • Elastic Potential
  • Electrostatic
  • Magnetic
  • Nuclear
• Kinetic energy store


  Energy of anything moving
• Thermal energy store


  Energy of any object, the hotter it is the more energy it has
• Chemical energy store


  Energy that can be released by a chemical reaction
• Gravitational Potential energy store

  Energy of anything in a gravitational field
• Elastic Potential energy store


  Energy of anything stretched
• Electrostatic energy store


  Energy of two charges that attract or repel each other
• Magnetic energy store


  Energy of magnets that attract or repel each other
• Nuclear energy store


  Energy released from atomic nuclei in nuclear reactions
• Ways energy can be transferred

  • Mechanically
  • Electrically
  • By Heating
  • By radiation
• Energy can be stored, transferred between stores and dissipated - but can never be created or destroyed. The total energy of a closed system has no net change.
• Energy is only useful when transferred from one store to another useful one. Some input energy can be lost or wasted when transferring, the less energy wasted the more efficient the device is said to be.
• Efficiency


  (Useful energy Output/Total Energy Output) x 100
• The wasted energy that's output by a device is transferred to less useful stores normally by heating or by light or by sound. As the energy is transferred away from the device to its surroundings the energy often spreads out and becomes less concentrated - we say it dissipates.
• According to the principle of conservation of energy the total amount of energy stays the same so the energy is still there but it can't be easily used or collected back again.
• Work


  When a force moves an object through a distance, work is done on the object and energy is transferred, measured in Joules
• Power


  The rate at which energy is transferred, measured in Watts
• Kinetic energy store


  Energy of anything moving, depends on mass and speed
• Gravitational Potential energy store

  Energy required to lift an object in a gravitational field, depends on mass, height lifted and gravitational field strength
• When there is no air resistance, energy lost from Gravitational Potential Energy store = Energy gained in Kinetic Energy store.
• With air resistance acting on falling objects, energy can be transferred to other stores such as the thermal energy stores of the object and surroundings.
• Sankey Diagram


  A diagram which makes it easy to see how much of the input energy is being useful and how much is being wasted, with the thickness of arrows representing the amount of energy
• Methods of heat transfer

  • Conduction
  • Convection
  • Radiation
• Conduction


  The action of energy passing from one particle to another
• Convection


  When energy is carried from a hot place to a cold place (Dissipation)
• Radiation


  The transfer of energy through electromagnetic/infrared waves
• Conduction and convection do not work as well with an insulating layer, not allowing heat to be lost by convection or transferred through conduction.
• Black object will absorb IR waves whilst white reflects the IR
• Black will absorb and release more heat than a white jacket
• Types of Energy Sources

  • Non-renewable (fossil fuels, nuclear)
  • Renewable (wind, geothermal, solar, wave, tidal, hydroelectric, pumped storage)
• Energy harvesting from fossil fuels

  1. Chemical energy stores

  2. Thermal energy store of water by heating

  3. Water boils to form steam

  4. Steam turns a turbine

  5. Turbine transfers energy mechanically to kinetic energy store

  6. Generator turns with turbine producing electric current
• Fossil fuels


  • Will run out one day
• Nuclear (Uranium)


  • Energy transferred from nuclear energy stores to thermal energy stores by heating, then mechanically to kinetic energy stores (SAME METHOD AS FOSSIL)
• Advantages of fossil fuels

  • Cheap
  • Does not rely on external factors (e.g. weather)
• Disadvantages of fossil fuels

  • Release CO2
  • Will eventually run out
• Advantages of nuclear


  • Doesn't produce greenhouse gases
• Disadvantages of nuclear


  • Radioactive waste produced
  • Risky due to leaks
  • Cost money to set up
• Wind farms


  • Skip the boiling step and use wind to turn the turbine
• Advantages of wind


  • No pollutants
  • Cheap to run
• Disadvantages of wind


  • Noisy
  • Cost to set up
  • Need a lot to get a lot of energy