Translations of Encyclopedia about Physics

The word energy is derived from the Greek word of energeia, which refers to an acting force. Energy is work stored in a system or the capacity to perform such work. It is constant like an atom’s mass and cannot be created nor destroyed. Energy is used to describe various phenomena and, from a physics point of view, energy is the basic component of every matter.

Not only can energy occur in many forms, such as kinetic, heat, mechanical, electrical or nuclear energy, but it can also change forms. The work executed by a certain system or into which a certain amount of energy is inputted is measured in joules (J) or kilowatt-hours (kWh).

Energy is released with the fission or partitioning of chemical bonds and comes from the amount of energy contained in the individual elementary particles within atoms.

The atom is the smallest chemical element which cannot be broken down any further by chemical means. The particular construction of each atom, which is made of a positively charged nucleus and negatively charged layer of electrons, dictates the physical behaviour of atoms in individual elements. At the start of the 20^th century (1911), Ernst Rutherford and Niels Bohr formulated the first notion of an atom, comparing the structure of the solar system to the structure of an atom. According to their mobile, negatively charged planets (electrons) circulate along defined orbits around a positively charged sun (the nucleus of an atom). But, with the arrival of new information, this concept was abandoned, although their model remained an important building block for later atom models.

Energy is required for all equipment to operate. Without energy, the economic activity of every nation would collapse. For this reason, every country makes long term plans to meet its energy requirement, striving to take advantage of raw materials within its boundaries to limit its energy imports.

At present, important raw materials for generating energy are oil, natural gas and, in many countries, atomic energy. However, the transformation of these primary energy sources into a secondary energy source is associated with certain risks for mankind and nature. Besides that, these natural sources of energy are nonrenewable and can be eventually expended. Other sources of energy, which are not in such broad use but which are much friendlier to the environment, are water, wind, biomass, biogas and sun energy.

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