Scientists Say: Watt

This word is a measure of energy use


This light bulb is a “40 watt” model. It uses 40 joules of energy per second.

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Watt (noun, “WAHT”)

This is a unit used to measure the rate of energy use. It is amount of energy being continuously converted from one form to another.  A watt equals one joule (a standard unit of energy) per second. The watt is named after James Watt, who invented the steam engine. Energy use in daily life is usually measured in kilowatt-hours — hourly increments of 1,000 watts.

In a sentence

A cow-poop-based power plant on a college campus continuously produces 400 kilowatts, enough to power more than 250 homes.

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Power Words

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joule  The amount of energy needed to produce one watt for one second. Joule is a standard unit of energy.

watt    A measure of the rate of energy use, flux (or flow) or production. It is equivalent to one joule per second. It describes the rate of energy converted from one form to another — or moved — per unit of time. For instance, a kilowatt is 1,000 watts, and household energy use is typically measured and quantified in terms of kilowatt-hours, or the number of kilowatts used per hour.

Bethany Brookshire was a longtime staff writer at Science News Explores and is the author of the book Pests: How Humans Create Animal Villains. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

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