Energy

• A Closed System


  A system that does not exchange matter or energy with its surroundings.
• Conversation of Energy


  The law that energy can be transferred, stored or dissipated but never created or destroyed.
• Efficiency

  The ratio of useful output energy transfer to total energy input.
• Elastic Potential Energy


  The store of energy that stretched or compressed objects experience. It is directly proportional to the stiffness constant and to the square of the extension or compression.
• Fossil Fuels


  • Coal
  • Oil
  • Gas
• Gravitational Potential Energy


  The store of energy that all raised matter has. It is directly proportional to the mass of the object, the distance that it is risen and the gravitational field strength at that point.
• Joule


  Unit for Energy
• Kinetic Energy


  The store of energy that all moving matter has. It is directly proportional to the object’s mass and to the square of its velocity.
• Power 


  The rate at which energy is transferred, or at which work is done.
• Renewable Energy Resources 


  An energy resource that can be replenished whilst it is being used.
• Specific Heat Capacity 


  The amount of energy required to raise the temperature of 1kg of a substance by 1°C.
• Spring Constant 


  A measure of a spring’s stiffness. The greater the value, the greater the force required to stretch or compress the spring by a given distance.
• System


  A single, or group, of objects
• Thermal Conductivity


  The higher this value is for a given material, the higher the material’s rate of energy transfer via conduction will be.
• Waste Energy

  Energy that isn’t usefully used for the purpose of the system.
• Watt


  A unit of power. One Watt is equivalent to one joule of work being done in one second.
• Work Done 


  The energy transferred when a force acts over a distance.
• Renewable Energy Sources

  • Biofuel
  • Geothermal
  • Wave Power
  • Hydroelectric
  • Solar Power
  • Tidal Power
  • Wind Power
• Advantages of Renewable Energy Sources 


  • Can be Replenished
  • Reduces Carbon emissions
  • does not contribute to global warming
  • Creates Jobs
• Disadvantages of Renewable Energy Sources 


  • High Cost
  • Requires a lot of space
• Name the 8 energy stores 


  • Thermal
  • Kinetic
  • Gravitational Potential
  • Elastic Potential
  • Magnetic
  • Electrostatic
  • Nuclear
  • Chemical
• The 4 ways energy is transferred

  • mechanically
  • electrically
  • heating
  • radiation/waves
• If a subject is moving which store does it have energy in 


  Kinetic
• Describe the energy transfer when a moving car slows down

  Energy is transferred mechanically from the kinetic store to the thermal store.
• Describe the energy transfer when an electric kettle is used to heat water

  the electric current is a kettle transfers energy to the heating element's thermal store - energy is then transferred by heating from the heating element's thermal store to the thermal store of the water
• Describe the energy transfer when a battery powered toy car is used 


  energy is transferred electrically from the chemical store to the kinetic store of the car. Some energy is dissipated to the thermal store of the surroundings
• Name the unit that represents one joule transferred per second

  Watt
• What does a material's thermal conductivity tell you


  how well it conducts heat
• Which materials have low thermal conductivity?


  thermal insulators
• Give three factors that determine the rate of thermal energy transfer through a material


  • thermal conductivity of material
  • temperature difference
  • thickness of material
• What is infrared radiation?


  type of electromagnetic radiation
• What is the relationship between the temperature of an object and its emission of infrared radiation?


  It is directly proportional
• What is a black body?


  theoretical object that absorbs 100% of the radiation that falls on it, and does not reflect or transmit any radiation
• Name three greenhouse gases 


  • water vapour
  • carbon dioxide
  • methane
• Why do greenhouse gases increase the Earth's temperature


  Earth's surface absorbs and re-emits radiation from the sun, which greenhouse gases then absorb - they re-emit this radiation back towards the Earth's surface