Kristy Livingston, age 14, of Galveston, Texas, for her question:

WHAT IS A JOULE?

A joule is a unit of energy that is used to measure the amount of work done. It is named in honor of the British scientist James Joule. Here's how you pronounce the word: "jool."

One joule of energy equals 10 million ergs, or about 0.74 foot pound. It is equal to the energy needed to send an electric current of one ampere through a circuit of one ohm resistance. The use of one joule in one second is equal to one watt.

In 1894, the Congress of the United States made the joule a legal unit of measure.

The joule is too small an amount of energy for commercial measurement. Kilowatt hours are used instead.