# Help Zone

### Student Question

Secondary V • 1yr.

Why can't we create energy? How do power plants work if they don't create electricity?

Physics

## Explanations (1)

• Explanation from Alloprof

Explanation from Alloprof

This Explanation was submitted by a member of the Alloprof team.

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Team Alloprof • 1yr.

In fact, one cannot create energy because of the law of conservation of energy. We owe Lavoisier the simplest expression of this law, according to which:

"Nothing is lost, nothing is created, everything is transformed!"

Indeed,even though this may seem counterintuitive, all reactions in a single system (a place in which no energy escapes) are either transferred or energy transferred reactions. The total amount of energy is always the same, although the form of the energy may change.

This property of energy can be very useful in calculations, especially if we know the total amount of energy in a system as well as the amount of each kind of energy except one. In these kinds of situations, one only has to subtract the energy of each kind of energy from the total energy. The difference is the amount of energy, or the amount of energy that’s missing. More concretely, if A, B and C are quantities of different kinds of energy and T is the total quantity of energy, we can find the value of A if B, C and T are known:

$$A + B + C = T$$

$$A + 50kJ + 100kJ = 200kJ$$

$$A = 200kJ − 100kJ − 50kJ = 50kJ$$

Thus, in the closed system that is the Earth, power stations only transform different types of energy into electrical energy. For example, hydroelectric power stations transform the kinetic energy of water into electrical energy. They do not create electricity, but simply make the water-powered turbines move in order to generate an electric current.

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