The Cyber Home of Watman Associates Well hello, I'm Tom Watson, I am a System's Design, and Program Engineer at Watman Associates. I've put together this page as a page of the units of energy or power and work. In todays world many social environmental and political decision effecting the future course of society are being discussed. As an Engineer, I decided to put together a page on information on the units of energy. Unless one understands the units of measurement of energy or power and work one can not judge accurately the scale and scope of the problem and the solutions. If one cannot have a scale of comparison then one is just making a guess. It does not seem very wise to plan for the future on a guess or flip of a coin

Measuring Energy


There are many ways to measure energy.

  • Energy is defined as the equivalent of, or the capacity to do work.
  • Power is a measure of the amount of energy spent over a certain period of time.

    ENERGY UNITS AND POWER

  • The Joule (J) is the amount of energy needed to move a mass of 1kg through one meter with and acceleration of 1 meter per second per second.

  • The erg is the amount of energy needed to move a mass of 1gram through one cm with and acceleration of 1 cm per second per second.

  • The calorie (cal) is the amount of energy needed to raise the temperature of one gram of water 1 degree Centigrade (or Celsius) from 14.5C to 15.5C (58.1F to 59.9F)

  • The British Thermal Unit (BTU) is the amount of energy needed to raise the temperature of one pound of water from 60F to 61F (15.5C to 16.1C)
    NOTE: The specific heat of water varies slightly with temperature.

  • The Watt(W) (tom's favorite) is the power provided when one joule is used for one second. 1000 of tom's favorite are know as a kilowatt (kW).

  • The kilowatt hour (kWh) is the energy expended when 1000 of tom's favorites, a kilowatt is available for 1 hour.

  • The British horsepower (hp) is the power needed to raise 550 lb one foot in one second.

  • The metric horsepower is the power needed to raise 75kg one meter in one second. (But tom does not know what a metric horsepower meters anyway.)


    Now one can also express the relationship or conversions of one unit into another.

    Unit Equivalents
    1J 1 million erg
    1erg 1 millionth J
    1cal 4.1855J
    1000cal 1 kilocalorie or 1 Calorie
    1Btu 1054.7W
    1W 0.001341hp
    1hp 745.7W
    1hp metric 735.5W

    The next table gives the energy of the very small to the very large.

    The Energy of things and events. Joules
    The energy of a photon within the visible spectrum.2.5 X 10e-19J to 5.1 X 10e-19J
    0db sound for 1 second on a person's eardrum.10e-17J
    The rest mass energy of an electron.8.2 X 10e-14J
    Energy released for each fuzed atom of helium.4.3 X 10e-12J
    Energy released by spliting an atom of uranium.4 X 10e-11J
    1 erg1 X 10e-7J
    Moonlight on a persons face for one second.8 X 10e-5J or 800 erg
    Wingbeat of a honeybee.8 X 10e-4J or 8000 erg
    Chirrup of a cricket.9 X 10e-4J or 9000 erg
    Depressing the key of a manual typewriter.10e-1J or 100,000 erg
    1 cal4.1855J
    Lethal dose of Xrays.7 X 10e2 or 167 cal.
    Burning match.4 X 10e3J or 955 cal
    1 Btu 1054.5J
    1000 cal4185.5J or 1 Calorie or 3.96 Btu.
    Energy in a slice of Apple Pie.1.5 X 10e6J or 358.3 Calorie
    Woman running for one hour1.8 X 10e6J or 430.0 Calorie
    Man running for one hour2.5 X 10e6J or 597.3 Calorie
    Energy Contained in 1lb of Coal.1.5 X 10e7J or 3583 Calorie or 14224 Btu
    A day's heavy manual labor.1.7 X 10e7J or 4061 Calorie
    Explosion of 1 Short ton of TNT.4.2 X 10e9J
    Energy generated by Saturn V rocket.1.3 X 10e11J
    Atomic Bomb dropped on Hiroshima.8.4 X 10e13
    Hurricane.4 X 10e15J
    100Mt thermonuclear bomb.4.2 X 10e17J
    Earthquake Richter 8.10e18J
    Eruption, 1883 Krakatoa.6 X 10e18J
    Earth's Annual Share of solar radiation.5.6 X 10e24J
    Earth spinning on it axis.3 X 10e39J
    Earth traveling in orbit.2 X 10e33J
    Annual energy output of the Sun10e34J
    Supernova.10e41J

  • For any looking for more information on learning more about Physics there are numerous sources. Phil Rubin of the Department of Physics at the University of Richmond has a wonderful set of notes online.
  • General Physics I
  • General Physics II

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    Monroe CT 04668
    203 268 6728

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