What is the law of conservation of energy

In physics, the term conservation refers to something which doesn't change. This means that the variable in an equation which represents a conserved quantity is constant over time. It has the same value both before and after an event.

The Law of Conservation of energy basically says that energry cannot be destroyed or created (usually in a chemical reaction) but it can only be changed or transformed into another form.

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An example would be if you plug in a standing fan. The electrical energy from the wall socket is transformed into mechanical energy when the blades move. The electricity doesn't just disappear.

It should be d if not then c