`lŏmz), in physics, law stating that the electrostatic force between two charged bodies is proportional to the product of the amount of charge on the bodies divided by the square of the distance between them. If the bodies are oppositely charged, one positive and one negative, they are attracted toward one another; if the bodies are similarly charged, both positive or both negative, the force between them is repulsive (see charge charge, property of matter that gives rise to all electrical phenomena (see electricity ). The basic unit of charge, usually denoted by e, is that on the proton or the electron ; that on the proton is designated as positive (+e..... Click the link for more information. ). Coulomb's law applies exactly only when the charged bodies are much smaller than the distance separating them and therefore can be treated approximately as point charges. When combined with principles of quantum physics, Coulomb's law helps describe the forces that bind electrons to an atomic nucleus, that bind atoms together into molecules, and that hold together solids and liquids. The law was deduced in 1785 by C. A. de Coulomb Coulomb, Charles Augustin de (k
`lŏm, k..... Click the link for more information. from experimental measures of the forces between charged bodies; the experiments were made using his torsion balance.
Coulomb's law
Law formulated by C.-A. de Coulomb that describes the electric force between charged objects. It states that (1) like charges repel each other and unlike charges attract each other, (2) the attraction or repulsion acts along the line between the two charges, (3) the size of the force varies inversely as the square of the distance between the two charges, and (4) the size of the force is proportional to the value of each charge.
Coulomb's law [′kü′lämz ‚lȯ]
Coulomb's law
For electrostatics, Coulomb's law states that the direct force F of point charge q1 on point charge q2, when the charges are separated by a distance r, is given by F = k0q1q2/r2, where k0 is a constant of proportionality whose value depends on the units used for measuring F, q, and r. It is the basic quantitative law of electrostatics. In the rationalized meter-kilogram-second (mks) system of units, k0 = 1/(4 πε0), where ε0 is called the permittivity of empty space and has the value 8.85 × 10-12 farad/m. Thus, Coulomb's law in the rationalized mks system is as in the equation below,
The direction of F is along the line of centers of the point charges q1 and q2, and is one of attraction if the charges are opposite in sign and one of repulsion if the charges have the same sign. For a statement of Coulomb's law as applied to point magnet poles.
Experiments have shown that the exponent of r in the equation is very accurately the number 2. Lord Rutherford's experiments, in which he scattered alpha particles by atomic nuclei, showed that the equation is valid for charged particles of nuclear dimensions down to separations of about 10-12 cm. Nuclear experiments have shown that the forces between charged particles do not obey the equation for separations smaller than this. See Electrostatics
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