Energy

• Conservation of Energy

  Energy can be transferred, stored and dissipated (wasted), but can't be created or destroyed
• In a closed system, the net change in energy will always be zero
• Useful energy


  The energy that transfers to the intended store
• Wasted energy


  The energy transferred to other stores that has been dissipated
• Useful and wasted energy always add up to the energy input because energy cannot be created or destroyed
• Reducing wasted energy


  • Thermal insulation
  • Lubrication
• Thermal insulation


  Covering an object in a layer or multiple layers of a material to reduce the rate of heat transfer out of the object
• Lubrication


  Making the surfaces smoother to reduce the amount of energy lost to friction
• Thermal conductivity


  How well a material transfers heat energy through
• Materials with low thermal conductivity transfer less heat energy and are good insulators
• Materials with high thermal conductivity transfer more heat energy and are bad insulators
• Uses of electrical appliances

  • Heating
  • Lighting
  • Making objects move
  • Producing sound and visual images
• An electrical appliance is designed for a particular purpose and should waste as little energy as possible
• Specific heat capacity


  The amount of energy needed to increase the material's temperature
• Kinetic energy


  Stored in moving objects
• Magnetic energy


  Stored by two attracting or repelling magnets
• Thermal energy


  Stored due to the heat of an object
• Chemical energy

  Stored by chemical bonds
• Elastic potential energy


  Stored in an object that's been stretched or squashed
• Electrostatic energy


  Stored in two attracting or repelling charges
• Gravitational potential energy


  Stored in objects lifted to a height
• Nuclear energy


  Stored in the nuclei of atoms
• Energy transfers


  • Mechanical
  • Heating
  • Electrical
  • Radiation
• Closed system


  Energy can neither enter nor leave the system, so the total energy remains the same
• Open system


  Energy can be transferred into or out of the system
• Work done


  The amount of energy transferred when a force causes something to be displaced (moved)
• Power


  The rate at which energy is transferred or work is done
• Efficiency


  How much energy is transferred to useful energy and how much is wasted
• Reducing wasted energy increases the efficiency of an energy transfer
• Renewable energy sources


  • Solar power
  • Wind power
  • Geothermal power
  • Hydroelectric power
  • Wave power
  • Biofuels
• Non-renewable energy sources


  • Coal
  • Oil
  • Gas
  • Nuclear fuel
• Specific heat capacity


  The amount of energy needed to raise the temperature of 1 kg of a substance by 1 degree Celsius
• To improve the reading from the thermometer, add a few drops of water in the hole with the thermometer to improve thermal contact and ensure even heating
• Record the temperature value every 10 minutes from when the heater is inserted and switched on
• Plot a graph of temperature against work done by the heater, which should be a straight line initially
• Gradient of the graph

  Represents the inverse of the heat capacity for the metal block
• Specific heat capacity


  The heat capacity measured for a mass of 1 kg
• The difference between heat capacity and specific heat capacity is that specific heat capacity is the heat capacity measured for a mass of 1 kg