Energy is defined as the capacity of a body for doing work. The SI unit of energy is the joule. 1 joule is the work done by a force of 1 newton moving a distance of 1 metre in the direction of the force.

The product of power (watts) and duration (seconds). One watt second = one Joule.

All forms of energy fall into two categories, potential and kinetic energy. We can organise different forms of energy within these two categories.

Potential Energy

Stored energy and energy of position.

  1. Chemical Energy
  2. - stored in the bonds of atoms and molecules - coal, petrol, biomass.
  3. Gravitational Potential Energy
  4. - the energy of place or position.
  5. Nuclear Energy
  6. - energy stored in the nucleas of an atom.
  7. Stored Mechanical Energy
  8. - stored in objects through the application of force - springs.

Kinetic Energy

This is motion, motion of atoms, molecules, objects or waves.

  1. Electrical Energy
  2. - movement of electrons.
  3. Motion
  4. - movement of objects.
  5. Radiant Energy
  6. - electromagnetic energy - light, x-rays, gamma rays and radio waves.
  7. Sound
  8. - movement of energy through substances in longitudinal waves.
  9. Thermal Energy
  10. - the internal energy in substances - the vibration of atoms and molecules within substances.

1 calorie=4.1868 joules 1 kilowatt hour=3.6x106 J
1 therm (EEC)=105.506x106 J 1 therm (US)=105.4804x106 J
1 thermie=4.185407x106 J 1 ton of TNT4.184x109 J

Electron rest energy8.187x10-14 J
Neutron rest energy1.505x10-10 J
KE of a car (1500kg) at 100km/hr5.79630x105 J
1 ton of TNT4.184x109 J
Magnitude 10 Earthquake6.3x1022 J


A unit used in the natural gas industry for one million cubic feet of gas equivalent (cfe).

This is a unit of energy equal to about 1.091 terajoules (GJ).

See also: Approximate Energy, Barrel of Oil Equivalent, Calorie, Conservation of Energy, Efficiency, Energy Accounting, Energy Balance, Energy Conservation, Energy Efficiency, Energy Intensity, Energy Source, Energy Storage, First Law of Thermodynamics, Gravitational Potential Energy, Hartree, Interaction Energy, Internal Energy, Joule, kiloWatt hour, Kinetic Energy, Latent Energy, Life Cycle Analysis, Mechanical Energy, Renewable Energy, Sensible Energy, Therm, Tonne of Oil Equivalent, Vacuum Energy, Watt Hour, Work.

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Subjects: Physics

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