Feature Report: Measuring Energy

4 items of content in this feature report

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Units of Measurement for Secondary Energy Sources

Whatever its source, secondary energy (or energy carriers) can be quantified by a number of units that are widely used for electricity and heat.

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Electrical power (measured in watts) equals voltage (measured in volts) times current (measured in amps). © AFP

Measuring Heat

  • The jouleA derived unit of energy, work or amount of heat in the International System of Units. Its symbol is J... (J) is an SI unit. It is the universal unit for quantifying energy, whether in the form of work (the movement of a mass propelled by a force) or heatIn the field of statistical thermodynamics today, heat refers to the transfer of the thermal agitation of the particles making up matter... . The joule is a very small unit unsuitable for measuring large amounts of energy. This is why its multiples are more frequently used, such as the gigajoule (GJ), where 41.855GJ = 1 toe.
  • The calorie (cal), sometimes used to measure a quantity of heat, is a non-SI unit. A calorie is the quantity of heat required to raise the temperature of one gram of water by one degree Celsius under normal atmospheric conditions of 1013.25 hPa from a standard initial temperature of 15°C. The thermie (th) — a multiple of the calorie, equal to 1 million calories — is sometimes used by heating engineers in Europe.
  • The British Thermal Unit (BTU) is used in the United Kingdom. It corresponds to the quantity of heat required to raise the temperature of a pound of water by 1 degree Fahrenheit (°F). This is equivalent to heating 450 grams of water under normal atmospheric pressure of 1013.25 hPa from a standard initial temperature of 58.1°F, or 14.5°C.

The Watt, Used to Measure Electricity