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How Is Energy Measured?

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We measure energy in many different ways and for many different purposes. Quantities of energy given in one unit can always be converted to any other unit of energy. For example, 1 gram calorie is equivalent to 4.186 joules, which is used to measure heat energy.

Many people are familiar with kilogram calories, which are often used to measure the energy available in food. One calorie is the amount of energy needed to raise the temperature of one kilogram of water by one degree Celsius. When you see calories on the back of a package, they indicate the total amount of food energy in that item.

This illustrative explainer is featured in our Energy e-book series. Click on the thumbnails below to download our free e-books or subscribe to our iTunes U course. You can also visit our e-books page to view our other offerings.

Energy e-book cover 2013_4

Examine the science of energy, from what it is to where it comes from.

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Energy e-book cover 2013_4

Explore how humans use energy — from generating electricity to developing energy-efficient technologies.

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