Energy Basics

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Need to Know

  • What is the difference between energy and power?
  • Approximately how much energy is consumed by different activities?
  • How much energy does it take to run the world?
  • Where do we get our energy?

Energy is the ability to do work.

A joule is the SI unit of energy.

  • A joule is the energy transferred when a force of one newton moves an object one meter (1 newton meter)
  • 1 joule of energy is used in lifting a 1 kilogram brick (2.2 pounds) 10 centimeters (3.9 inches).
  • A kilowatt-hour is a unit of energy.
  • Running a 1.2 kilowatt microwave for 1 hour uses 1.2 kW-h of energy. That’s 4.3 megajoules or 4,300,000 joules.
  • A calorie is the heat energy required to increase 1 gm of water 1 deg C. (4.1868 J)

A watt is a unit of power.

  • Power is how fast energy is used or produced.
  • A watt (W) is a joule (J) of energy used or produced per second.
  • In 2010, the average US power use was 3.3 terawatts, or 3,300,000,000,000 watts.
  • 1 horsepower (hp) is 745.7 watts.

Power consumption of devices compared

Energy Consumption by Source