Energy Transfers and Resources

• Energy transfers


  • Energy can be transferred usefully, stored or dissipated (spread out to the surroundings)
  • Energy cannot be created or destroyed
• In a closed system the total energy never changes, but it can be transferred from one store to another
• Electricity-powered lift raises the lift carriage

  1. Transfers electrical energy into gravitational potential energy

  2. Some energy is dissipated into the surroundings as heat and sound

  3. Wasted energy is no longer available for useful transfers
• Wasted energy

  Caused by unwanted energy transfers
• Reducing unwanted energy transfers

  1. Lubrication - reduces the friction that produces heat

  2. Tightening any loose parts - prevents unwanted vibration that wastes energy as sound

  3. Thermal insulation - reduces heat loss
• A system isn't always a single device; it could be an entire building
• A building loses heat to the surroundings

  The building cools down
• Rate of cooling

  Depends on the thickness and thermal conductivity of the walls
• Thin walls with high thermal conductivity will conduct heat the quickest and the building will cool down rapidly
• Object projected upwards

  • Kinetic energy (from the initial movement of the object) to gravitational potential energy (from its increase in height)
• Object hitting an obstacle

  • Kinetic energy (from the moving object) to thermal energy and sound (when the object hits the obstacle)
• Car accelerating

  • Chemical energy (in the fuel) to kinetic energy (the movement of the car)
• Car braking

  • Kinetic energy (from the movement of the car) to thermal energy (from friction in the brakes)
• Water boiling in a kettle

  • Electrical energy to thermal energy
• What is a key point to remember about an anomalous result?

  An anomalous result is one that doesn't fit the pattern. These:

  . should be looked at to try and determine the cause

  . should be ignored when plotting graphs

  . should not be included when calculating averages
• Main uses for energy resources

  • Transport
  • Electricity generation
  • Heating
• Energy resources

  • Renewable energy resources, which can be replenished
  • Non-renewable energy resources, which will eventually run out
• Energy resource categories

  • Renewable
  • Non-renewable
• Renewable - Biofuel

  • Main uses: Transport and electricity generation
  • Environmental impacts: Large areas of land are needed for growing fuel crops. This can be at the expense of food crops in poorer countries
• Renewable - Wind

  • Main uses: Electricity generation
  • Environmental impacts: Does not provide a constant source of energy. Turbines can be noisy/dangerous to birds. Some people think they ruin the appearance of the countryside
• Renewable - Water (hydro-electricity)

  • Main uses: Electricity generation
  • Environmental impacts: Requires large areas of land to be flooded, altering ecosystems and displacing the people that live there
• Renewable - Geothermal

  • Main uses: Electricity generation and heating
  • Environmental impacts: Only available in a limited number of places where hot rocks can be found close to the surface, e.g. Iceland
• Renewable - Tidal

  • Main uses: Electricity generation
  • Environmental impacts: Variations in tides affect output. Have a high initial set-up cost. Can alter habitats/cause problems for shipping
• Renewable - Solar

  • Main uses: Electricity generation and some heating
  • Environmental impacts: Depends on light intensity, so no power produced at night. High cost in relation to power output
• Renewable - Water waves

  • Main uses: Electricity generation
  • Environmental impacts: Output depends on waves, so can be unreliable. Can alter habitats
• Non-renewable - Nuclear fuel

  • Main uses: Electricity generation and some military transport
  • Environmental impacts: Produces radioactive waste but no other emissions. Costly to build and decommission. Reliable output
• Non-renewable - Coal

  • Main uses: Electricity generation, heating and some transport
  • Environmental impacts: Burning produces greenhouse gases (CO2) and contributes to acid rain (SO2). Reliable output
• Non-renewable - Oil

  • Main uses: Transport and heating
  • Environmental impacts: Reliable output. Provides a compact source of energy for transport. Burning produces CO2, NO2 and SO2. Serious environmental damage if spilt
• Non-renewable - Gas

  • Main uses: Electricity generation, heating and some transport
  • Environmental impacts: Reliable output. Burning produces CO2 but not SO2