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What is energy?

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Quick answer

Energy is the capacity to do work — to move, heat, light, or change things. It comes in many forms (kinetic, heat, light, chemical, electrical) and can be converted between them, but it can never be created or destroyed, only transformed.

Key things to understand

  1. Energy is the ability to cause change or do work, measured in joules (J).
  2. It takes many forms: kinetic (motion), potential (stored), thermal (heat), chemical, electrical, and nuclear.
  3. The law of conservation of energy says energy can't be created or destroyed — only changed from one form to another.
  4. Energy constantly converts: food (chemical) → motion (kinetic), or sunlight → electricity in a solar panel.
  5. Power is how fast energy is used or transferred, measured in watts.

People also ask

What are the main types of energy?
Common forms include kinetic (motion), potential (stored position), thermal (heat), chemical, electrical, light, and nuclear — and they can convert into one another.
Can energy be created or destroyed?
No. The law of conservation of energy says the total stays constant — energy only changes form, such as chemical energy becoming motion and heat.
What's the difference between energy and power?
Energy is the total capacity to do work; power is how quickly that energy is used or delivered. A sprinter uses energy fast (high power); a marathoner spreads it out.

Part of the guide: Energy & Electricity at Home →