Energy Transfers

• Chemical Energy Store:

  The energy stored in chemical bonds.
• Kinetic Energy Store:

  The energy of a moving object.
• Gravitational Energy Store:

  The energy of an object at a height.
• Elastic Energy Store:

  The energy of a stretched or squashed object.
• Thermal Energy Store:

  The energy of a heated object.
• Magnetic Energy Store:

  The energy of repelling poles pushed together or attracting poles pulled apart.
• Electrostatic Energy Store:

  The energy of repelling charges pushed together or attracting charges pulled apart.
• Nuclear Energy Store:

  The energy stored in the nucleus of an atom.
• Mechanical Energy Transfer:

  A force moving an object through a distance.
• Electrical Energy Transfer:

  Charges moving due to a potential difference.
• Heating Energy Transfer:

  Due to a temperature difference caused electrically or by chemical reactions.
• Radiation Energy Transfer:

  Energy transferred as a wave.
• Principle of Energy:

  'Energy can't be created or destroyed, only transferred.'
• Efficiency Equation:

  Efficiency = (Useful energy output/Total energy output) * 100%
• Energy transfers example 1:

  'A toy car rolls to a stop.'

  Kinetic energy store -- Mechanical transfer--> Thermal energy store
• Energy transfers example 2:

  'An electric motor lifting a weight.'

  Chemical energy store -- Electrical transfer--> Gravitational energy store
• Energy transfers example 3:

  'Bringing water to boil on a gas hob.'

  Chemical energy store -- Heating transfer--> Thermal energy store
• Sankey Diagrams:

  • Starts off as one arrow
  • Splits into two or more points
  • Shows where the energy in a system will go to
  • Width of the arrow is total energy in that place
  • Straight arrow is useful energy
• CONDUCTION:

  The flow of heat energy from a region of high temperature to a region of low temperature, without movement of the actual material. The heat transfers via collisions of particles, passing on vibrations.
• CONDUCTION (details):

  • Occurs in solids, liquids and gases. Best in solids.
  • Best in metals, as the energy is transferred by the delocalised electrons (which can move freely) as well as with normal vibrations.
• CONVECTION:

  The flow of heat energy from a region of high temperature to a region of low temperature by the movement of a fluid. The hot particles take the place of the cold particles.
• CONVECTION (details):

  1. Water is heated, so the particles move further apart and become less dense.
  2. Hot water rises.
  3. Cool water flows in, replacing the hot water.
  4. Cool water heats, cycle repeats and a convection current is formed.
• RADIATION:

  The flow of heat energy from an area of high to low temperature by infrared radiation. Does not require particles. When infrared radiation is absorbed, the object is heated.
• SEA BREEZES (DAY):

  1. Land heats up quicker than the sea.
  2. Air above land is heated, expands and rises.
  3. Rising air is replaced by cooler air drawn in from the sea surface, so convection current is formed.
• LAND BREEZES (NIGHT):

  1. Land cools down quicker than the sea.
  2. Air above sea is heated, expands and rises.
  3. Rising air is replaced by cooler air drawn in from the land surface, so convection current is formed.
• EMISSION:

  Energy emitted from a source in the form of waves.

  A black surface emits more infrared radiation per second than a silver surface at the same temperature.
• ABSORPTION:

  Energy absorbed from another source in the form of waves.

  A black surface absorbs more infrared radiation per second than a silver surface at the same temperature.
• INSULATION:

  Trapped air is a good insulator (and a poor conductor). Hair, fur and feathers are also good insulators because they trap air. These also reduce heat loss from convection as there is no room for the air to flow. Double glazing (two layers with air trapped between them) also reduces heat loss by conduction and convection.