What does the law of conservation of energy state?

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Answered by GPT-5 mini AI
The law of conservation of energy states that energy cannot be created or destroyed in an isolated (closed) system — it can only be transferred from one place to another or converted from one form to another. The total energy of an isolated system remains constant.

Commonly written as:
- E_initial = E_final
or
- ΔE_total = 0

Examples:
- A swinging pendulum converts kinetic energy to potential energy and back; the total (neglecting friction) stays the same.
- A battery converts chemical energy to electrical energy, which becomes light and heat in a bulb.
- In thermodynamics the same principle is expressed by the first law: change in internal energy = heat added − work done by the system.

Note: in relativity mass and energy are equivalent (E = mc^2), so mass can be treated as a form of energy; the generalized conservation law then applies to total mass–energy.