energy

• Energy capacity of doing work
• Energy cannot be created or destroyed but it can be transferred, dispersed or stored in different ways
• Different energy stores

  • Mechanical
  • Magnetic
  • Thermal
  • Chemical
  • Elastic
  • Gravitational
• Energy store examples

  • Fridge magnet
  • Energy stored in chemical bonds
  • Energy of a moving object
  • Energy stored in compressed springs
  • Gravitational energy of an object at height
• Marginal energy

  Energy stored when repelling charges have been pushed further apart
• Potential energy


  Energy stored in the position of an object
• Kinetic energy

  Energy of a moving object
• Energy transfer types

  1. Mechanical work

  2. Electrical work

  3. Heating

  4. Radiation
• Power


  Rate at which energy is transferred
• Work done


  Work done = force x distance
• Work is done on an object when energy is transferred
• Efficiency

  Efficiency = useful energy transferred / total energy supplied
• Percentage efficiency

  Percentage efficiency = efficiency x 100
• Kinetic energy (KE)

  Energy of a moving object
• Gravitational potential energy (GPE)

  Energy an object has due to being raised above ground
• The greater the height above ground, the greater the GPE
• Kinetic energy is converted to GPE when a ball is thrown upwards
• GPE is converted to kinetic energy when falling downwards
• This follows the Law of conservation of energy
• Elastic potential energy

  Energy stored in a spring when work is done in compressing or stretching
• Spring constant

  A measure of how difficult it is to compress or stretch a spring
• energy is the ability to do work
• the units of energy are joules (J)
• energy is the ability to do work
• power is the rate at which energy is transferred or used up
• 1 kilowatt hour (kWh) = 3600 kJ
• An object's spring constant is a measure of how many Newtons of force it would require to stretch (or compress) the object by 1 metre. It has the units N/m.
• A higher spring constant means the spring is more firm (harder to stretch). A lower spring constant means the spring is less firm (easier to stretch).
• An object's gravitational potential energy is the energy it has due to its height in a gravitational field.
• Magnetic energy store: The energy stored when repelling magnetic poles are pushed closer together, or when attracting magnetic poles are pulled further apart.
• Gravitational potential energy (GPE) = Mass (m) x Gravitational field strength (g) x Height (h)