P1

• Energy


  The ability to do work
• Energy changes in a system

  1. When work is done by an object, energy is transferred from the object

  2. When work is done on an object, energy is transferred to the object
• Work done


  Energy transferred
• Energy and work done

  Measured in joules (J)
• 1 kJ


  1000 J
• Principle of conservation of energy


  The total amount of energy in a closed system is constant
• Energy stores


  • Kinetic
  • Chemical
  • Thermal
  • Gravitational potential
  • Magnetic
  • Electrostatic
  • Elastic potential
  • Nuclear
• Specific heat capacity


  The amount of energy required to increase the temperature of 1kg material by 1°C
• Power


  The rate at which energy is transferred or the rate at which work is done
• Required practical: How to measure the specific heat capacity of a material
• Equipment: thermometer, joulemeter or wattmeter, immersion heater, cylinder made from material, insulating material
• The cylinder would have reduced the amount of heat loss to the surroundings
• Conservation of energy


  Energy cannot be created or destroyed, it can only be converted from one form to another
• Energy dissipation


  Energy which is spread out or wasted (some loss to the surroundings)
• Energy dissipation is caused by air resistance, friction, and electrical resistance
• Ways to reduce energy dissipation

  • Lubrication
  • Using low resistance components
  • Insulating buildings
• Efficiency


  The ratio of the useful output energy to the total input energy
• Non-renewable energy resources


  • Coal
  • Oil
  • Gas
• Renewable energy resources


  • Biomass
  • Tidal
  • Hydroelectric
  • Nuclear
  • Wave
  • Wind
  • Solar
  • Geothermal
• Non-renewable resources are limited, fossil fuels contribute to global warming, nuclear has radioactive waste
• Renewable resources will never run out, are clean but can be unreliable or expensive