Energy

• Energy stores

  • Thermal
  • kinetic
  • Gravitational potential
  • Elastic potential
  • Chemical
  • Magnetic
  • Electrostatic
  • Nuclear
• Definition of power


  The rate at which energy is transferred
• State two equations for power

  Power= energy transferred/time

  Power= work done/time
• What is specific heat capacity?


  The amount of energy needed to raise the temperature of 1kg of a substance by 1 degrees celcius
• Equation for specific heat capacity

  change in thermal energy= mass x SHC x change in temperature
• Equation for elastic potential energy


  1/2 x Spring constant x extension squared
• Conduction


  The process where vibrating particles transfer energy to neighbouring particles

  occurs mainly in solids
• Equation for gravitational potential energy


  mass x gravitational field strength x height
• Convection


  When energetic particles move away from hotter to cooler regions

  occurs only in liquids and gases
• Efficiency equations


  Efficiency= useful output energy transfer/total input energy transfer

  Efficiency= useful power output/total power input
• Law of conservation of energy


  Energy can be transferred usefully, stored or dissipated but never destroyed
• How is energy transferred

  • Mechanically
  • Electrically
  • Heating
  • Radiation
• Equation for kinetic energy


  Kinetic energy= 1/2 x mass x (speed) squared
• How can the efficiency of a system be increased?

  1. Reducing waste output(by lubrication, thermal insulation)
  2. Recycling waste output(recycle waste energy as input energy)
• State three methods of reducing heat loss in a building

  1. Double glazing
  2. Loft and wall insulation
  3. Thicker walls
• How can the efficiency of a mechanical machine with moving parts be improved?

  Lubricate any moving parts to reduce the friction and therefore energy loss due to heating
• How can the efficiency of a radiator be improved?

  Installing metal foil sheets behind the radiator to reflect the heat back into the room rather than it being absorbed into the walls
• How can the efficiency of boiling water in a pan be improved?

  By placing a lid on the pan to reduce the heat loss from the top
• Renewable energy sources

  • Solar
  • wind
  • water waves
  • hydro electricity
  • bio fuel
  • tides
  • geothermal
• Renewable energy resource


  An energy source which can be replenished as it is being used up
• Non-renewable energy resource


  Fossil fuels (for example coal, oil and gas)
• Advantages of generating power using gas rather than coal

  • Flexible Generation: Gas power stations have short start-up times so can be switched on/off more readily
  • Lower emissions of carbon dioxide
• Disadvantages of using renewable energy resources to generate power


  • Output often determined by external factors (like wind speed), so supply is uncertain
  • Generating power through other means is often more efficient and economically beneficial
• Burning fossil fuels


  • Carbon Dioxide contributes to the greenhouse effect, and causes global warming
  • Sulphur Dioxide leads to acid rain, which can damage buildings and crops
• Advantages of fossil fuels as an energy resource

  • Reliable: Not dependent on external factors so can generate power anytime
  • Can produce large amounts of energy for a given quantity
  • Still relatively abundant, so cost-effective
• Advantages of nuclear power

  • Very large amounts of energy for relatively small quantities of fuel
  • Doesn't release greenhouse gases and so doesn't contribute to climate change
  • Low fuel costs
• Disadvantages of nuclear power

  • Produces nuclear waste which is harmful to humans & must be safely stored for centuries
  • Non-Renewable energy source
  • Risk of nuclear accidents, which have fatal consequences on humans and the environment
• How hydroelectric power produces energy

  1. Rainwater collects behind a dam

  2. When this water is released, it is used to turn a turbine

  3. This turbine turns a generator which produces electricity
• Disadvantages of using biofuels

  • When plants are burned or decay they release CO2
  • In order to grow biofuels, you need to destroy land which leads to problems because: The land could have been natural habitats, Destroying land may involve burning plants growing on it, which would release CO2
  • Growing biofuels reduces the land available for growing food
• Advantages of tidal energy sources

  • They do not produce greenhouse gases
  • They are quite reliable, as tides happen twice a day
  • They are cheap to run as tides are natural, and so are free
• Disadvantages of hydroelectric power

  • The dam may cause flooding
  • It can cost a lot to install the required infrastructure
• Advantages of solar panels


  • They don't cause harm to the environment
  • They are a renewable resource
  • They can be used in remote areas where other types of energy are less accessible
• Social factors which may act as a deterrent for certain types of energy production

  • Visual Pollution
  • Sound Pollution
• Chemical


  energy that can be transferred by chemical reactions involving foods, fuels, and the chemicals in batteries.
• closed system


  unable to exchange energy and matter with their surroundings
• dissipated


  wasted energy
• efficiency


  a measure of how much energy is transferred usefully
• elastic potential


  energy an elastic object has when it is stretched or compressed
• gravitational potential


  energy an object has because of its height above ground
• kinetic


  energy an object has because it is moving