We explain what the Principle of Conservation of Energy is, how it works and some practical examples of this physical law.
What is the Principle of Conservation of Energy?
He Energy Conservation Principle either Law of conservation of energyalso known as the First Law of Thermodynamics, states that the total amount of energy in an isolated physical system (that is, without any interaction with other systems) will always remain the same, except when it is transformed into other types of energy.
This is summarized in the principle that Energy in the universe can neither be created nor destroyed only transformed into other forms of energy, such as electrical energy into heat energy (this is how resistors operate) or light energy (this is how light bulbs operate). 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 their 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 work (W) done. by said system. That way, we have the formula: Q = ΔU + W from which it follows that ΔU = Q – W.
This principle also applies to the field of chemistry, since The energy involved in a chemical reaction will always tend to be conserved just like mass, except in cases where the latter is transformed into energy, as indicated by Albert Einstein's famous formula of E = mc2 where E is energy, m is mass and c is the speed of light. This equation is of utmost importance in relativistic theories.
Energy, then, is not lost, as has already been said, but it is may no longer be useful for performing work, according to the Second Law of Thermodynamics: the entropy (disorder) of a system tends to increase as time passes, that is, systems inevitably tend toward disorder.
The action of this second law in accordance with the first is what prevents isolated systems from existing that keep their energy intact forever (such as perpetual motion, or the hot contents of a thermos). Just because energy cannot be created or destroyed does not mean that it remains unchanged.
See also: Law of Conservation of Matter
Examples of the Principle of Conservation of Energy
Suppose there is a girl on a slide, at rest. Only gravitational potential energy acts on it, therefore its kinetic energy is 0 J. When sliding down the slide, however, its speed increases and so does its kinetic energy, but as it loses height, its gravitational potential energy also decreases. Finally, it reaches maximum speed right at the end of the slide, with its maximum kinetic energy. But its height will have decreased and its gravitational potential energy will be 0 J. One energy is transformed into another, but the sum of both will always give the same amount in the system described.
Another possible example is the operation of a light bulb, which receives a certain amount of electrical energy when the switch is activated and transforms it into light energy and thermal energy, as the light bulb heats up. The total amount of electrical, thermal and light energy is the same, but it has been transformed from electrical to light and thermal.
