# principle of conservation of energy

2022

We explain what the Principle of Conservation of Energy is, how it works and some practical examples of this physical law.

Potential energy is transformed into kinetic energy when we go down a slide.

## What is the Principle of conservation of energy?

The Principle of Conservation of Energy or Energy conservation law, also known as the First Principle of Thermodynamics, states that the total amount of Energy in an isolated physical system (that is, without any interaction with other systems) it will always remain the same, except when it is transformed into other types of energy.

This is summed up in the principle that the energy in the universe It can neither be created nor destroyed, only transformed into other forms of energy, such as electrical energy in caloric energy (this is how resistors work) or in light energy (this is how light bulbs work). Hence, when carrying out certain jobs or in the presence of certain chemical reactions, the amount of initial and final energy will appear to have varied if its transformations are not taken into account.

According to the Principle of Conservation of Energy, when introducing a certain amount of heat (Q) into a system, it will always be equal to the difference between the increase in the amount of internal energy (ΔU) plus the job (W) made by said system. In that way, we have the formula: Q = ΔU + W, from which it follows that ΔU = Q - W.

This principle also applies to the field ofchemistry, since the energy involved in a chemical reaction will tend to always be conserved, just like themass, except in cases where the latter is transformed into energy, as indicated by Albert Einstein's famous formula of E = m.c2, where E is energy, m is mass, and c isspeed of light. This equation is of utmost importance in relativistic theories.

Energy, then, is not lost, as has already been said, but it can cease to be useful to carry out work, according to the Second Law of Thermodynamics:entropy (disorder) of a system tends to increase as theweatherIn other words, systems inevitably tend to disorder.

The action of this second law in accordance with the first is what prevents the existence of isolated systems that keep their energy intact forever (such as the movement perpetual, or the hot contents of a thermos). That energy cannot be created or destroyed does not mean that it remains unchanged.

## Examples of the Principle of conservation of energy

Suppose there is a girl on a slide, at rest. Only one acts on it gravitational potential energy, therefore its kinetic energy is 0 J. As it slides down the slide, on the other hand, its speed increases and also its Kinetic energy, but when losing height, its gravitational potential energy also decreases. Finally, it reaches full speed right at the end of the slide, with its maximum kinetic energy. But his height will have decreased and his potential energy gravitational energy will be 0 J. One energy is transformed into another, but the sum of both will always yield the same amount in the system described.

Another possible example is the operation of a light bulb, which receives a certain amount of electric power by activating the switch and transforms it into light energy and in thermal energy, as the bulb heats up. The total amount of electrical, thermal and light energy is the same, but it has been transformed from electric to light and thermal.

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