What is the SI unit of energy?
AnswerJoule
Energy is measured in joules; a watt is one joule per second.
Science · Facts & stats
Energy facts & stats
7 fact-checked facts about energy sources, energy science and saving energy, each with the reason behind it. 5 more are in today's round and join this page after it closes.
The basics
Which of these is a renewable energy source?
AnswerWind
Wind is replenished naturally; fossil fuels take millions of years to form.
Going deeper
What does the law of conservation of energy say?
AnswerEnergy cannot be created or destroyed, only changed in form
Total energy in a closed system stays constant.
What fuel do most nuclear power plants use?
AnswerUranium
Most reactors split uranium atoms to release heat.
Compared with incandescent bulbs, LED bulbs use roughly how much less energy for the same light?
AnswerAt least 75% less
The US Department of Energy says LEDs use at least 75% less energy.
Expert level
What nuclear process powers the Sun?
AnswerFusion of hydrogen into helium
In the Sun's core, hydrogen nuclei fuse into helium, releasing energy.
The Three Gorges Dam, the world's largest hydropower plant by capacity, is in which country?
AnswerChina
It spans the Yangtze River in Hubei Province.
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