Scientists Say: Power

This word describes the rate at which energy is delivered or used to do work


Solar panels catch the sun’s rays to make electricity. Wind turbines generate electricity from the spinning blades. The word “power” describes the rate at which these devices make electricity. 

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Power (noun, “POW-urr”)

In physics, this word describes the rate at which energy is produced, used or delivered.  A rate is a measurement of one amount in relation to another. For example, speed is a rate. A car’s speed is the distance it moves divided by the time it takes to move that distance. That gives a rate of kilometers (or miles) per hour. 

Power is a rate that describes the time it takes to produce, consume or deliver energy. A battery supplies electrical energy. Its power is the energy it provides divided by the time it takes to deliver that energy. Energy is measured in units called joules. Its relation to time in seconds gives a unit of power called watts. A 40-watt lightbulb uses 40 joules of energy each second.

The word power can also be used to describe energy, usually in the form of electricity, that runs devices and machines. When used with words like solar, nuclear, coal and wind, power describes processes that are used to make electricity.

In a sentence

Scientists made a device that generates electric power from the temperature difference between Earth and the cold night sky.

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Carolyn Wilke is a former staff writer at Science News Explores. She has a Ph.D. in environmental engineering. Carolyn enjoys writing about chemistry, microbes and the environment. She also loves playing with her cat.

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