Energy Resources and Transfers - Physics

• Kinetic Store


  Anything moving has energy in this store
• Thermal Store


  The hotter an object is the more of this store it will have
• Chemical Store


  Anything that can release energy by a chemical reaction
• Gravitational Potential Store


  Anything in a gravitational field (an object that can fall)
• Elastic Potential Store


  Anything stretched, eg. springs and rubber bands
• Electrostatic Store


  Energy stored in electric charges that are attracting or repelling
• Magnetic Store


  Energy stored in magnets that are attracting or repelling
• Nuclear Store


  Energy stored in the nucleus of an atom
• Mechanical Energy Transfer


  An object moving due to a force acting on it
• Mechanical Energy Transfer Example


  Pushing, pulling, stretching or squashing
• Electrical Energy Transfer


  A charge moving through a potential difference
• Electrical Energy Transfer Example


  Charges moving around a circuit
• Heating Energy Transfer


  Energy transferred from a hotter object to a colder object
• Heating Energy Transfer Example


  Heating a pan of water on a stove
• Radiation Energy Transfer


  Energy transferred by light or sound waves
• Radiation Energy Transfer Example


  Light, microwaves, infrared waves
• The Law of The Conservation of Energy


  Energy cannot be created or destroyed, only transferred from one store to another
• Efficiency


  The proportion of useful output energy transferred from total input energy
• Efficiency Equation


  Efficiency = (Useful Energy Output / Total Energy Input) x 100
• Work Done Equation 1


  Work Done (W) = Energy Transferred (E)
• Work Done Equation 2


  Work Done = Force x Distance
• Gravitational Potential Energy Equation


  GPE = mass x gravitational field strength x height
• Kinetic Energy Equation


  KE = 0.5 x mass x (velocity)^2
• Power Equation


  Power = Work Done / time
• Power


  The rate of the transfer of energy or the rate of doing work
• How does the conservation of energy link between GPE, KE and Work Done?


  Because energy is conserved, the decrease in GPE = increase in KE, for a falling object if no energy is lost to the surroundings
• Conduction


  A transfer of heat between substances that are in direct contact with each other, mainly in solids
• Why are metals good conductors?


  They have free (delocalised) electrons that move about their structure, colliding with positive ions and transferring kinetic energy to them at a faster rate
• Conduction Model Answer

  1. The object's particles absorb heat energy (using the kinetic energy of the particles).
  2. They vibrate faster.
  3. This causes more collisions with neighbouring particles.
  4. These collisions pass on more energy from atom to atom.
• Convection


  Occurs in gases and liquids (fluids) and results in the creation of a convection current
• Convection Model Answer

  1. As the fluid is heated, the particles absorb heat energy and move faster.
  2. The fluid expands and becomes less dense, causing it to rise.
  3. As the fluid cools, it becomes more dense and begins to sink.
  4. This creates a convection current.
• Radiation


  All objects emit and absorb infrared radiation, which is on the EM spectrum. This means it can pass through a vacuumn.
• Good Conductors of Radiation


  Dark, matte, hot and large surfaces are ideal - this is why solar panels are black
• Bad Conductors of Radiation


  White, light and shiny surfaces are bad conductors but they are good reflectors
• Radiation Model Answer

  • Light, shiny surfaces reflect infrared radiation back towards the substance, preventing it from cooling down.
  • Matte black surfaces absorb/emit the infrared radiation, causing the substance to heat up/cool down.
• How do you reduce unwanted energy transfer in a house?


  * Cavity wall

  * Cavity wall insulation

  * Loft insulation

  * Double glazed windows
• Cavity Wall


  A gap between two brick walls contains air, which has a lower thermal conductivity than brick.
• Cavity Wall Insulation


  The gap between two brick walls is filled with material that has a lower thermal conductivity than air.
• Loft Insulation


  A thick layer of material with a low thermal conductivity reduces the rate of heat transfer through the ceiling.
• Double Glazed Windows


  A gap between two panes of glass contains air or another gas, which has a lower thermal conductivity than glass.