Physics - Energy

• Types of energy stores

  Thermal, Kinetic, Gravitational Potential, Elastic Potential, Chemical, Magnetic, Electrostatic, Nuclear
• What happens when a system changes?

  Energy is transferred.
• Closed system


  A system where energy and matter can't enter or leave.
• Kinetic energy equation

  Kinetic energy (J) = 1/2 x mass (kg) x speed^2 (m/s)
• Gravitational potential energy equation

  Gravitational potential energy (J) = mass (kg) x gravitational field strength (N/kg) x height (m)
• What happens when an object falls?

  Energy is transferred from its gravitational potential energy store to its kinetic energy store.
• Elastic potential energy equation

  Elastic potential energy (J) = 1/2 x spring constant (N/m) x extension^2 (m)
• Specific heat capacity


  The amount of energy needed to raise the temperature of 1 kg of a substance by 1°C
• Specific heat capacity equation

  Change in thermal energy (J) = mass (kg) x specific heat capacity (J/kg°C) x temperature change (°C)
• What equipment do you need to investigate specific heat capacity?


  Power supply, ammeter, heater, thermometer, block of material and insulation.
• Conservation of energy principle

  Energy can be transferred usefully, stored or dissipated, but can never be created or destroyed.
• Power


  The rate of doing work
• Power equation


  Power (W) = Energy transferred (J) / Time (s)
• Conduction


  Vibrating particles transfer thermal energy to neighbouring particles.
• Thermal conductivity


  How quickly energy is transferred through a material by conduction
• Convection


  The movement of particles due to differences in density that are caused by temperature variations
• Where does conduction occur?

  Solids
• Where does convection occur?

  Liquids and gases
• Lubrication


  This reduces friction which reduces dissipation of energy
• Thermal insulator


  A material that reduces or prevents the transfer of heat
• Types of thermal insulators

  Cavity walls, loft insulation, double glazed windows and draught excluders
• What types of thermal insulators reduce conduction?

  Cavity walls and double glazed windows
• What types of thermal insulators reduce convection?

  Loft insulation and draught excluders
• Efficiency equation


  useful output energy transfer/total input energy transfer
• Non-renewable energy resources

  Coal, oil, gas, nuclear fuel
• Renewable energy resources


  Solar, wind, water waves, hydro-electricity, bio-fuels, tides, geothermal
• Wind power


  The use of a windmill to drive an electric generator
• Solar power


  Energy from the sun that is converted into thermal or electrical energy
• Geothermal power


  Power obtained from underground thermal energy stores
• Hydro-electric power


  Electricity created by the energy of falling water
• Wave power


  Power produced from ocean waves that is used to turn an electrical generator
• Tidal power


  Electricity generated by the movement of sea water caused by the tides
• Work done = force x distance moved by object
• Weight = mass x gravitational field strength