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Coulomb's inverse-square law, or simply Coulomb's law, is an experimental law [1] of physics that calculates the amount of force between two electrically charged particles at rest. This electric force is conventionally called the electrostatic force or Coulomb force . [ 2 ]
Continuous charge distribution. The volume charge density ρ is the amount of charge per unit volume (cube), surface charge density σ is amount per unit surface area (circle) with outward unit normal n̂, d is the dipole moment between two point charges, the volume density of these is the polarization density P.
The coulomb was originally defined, using the latter definition of the ampere, as 1 A × 1 s. [4] The 2019 redefinition of the ampere and other SI base units fixed the numerical value of the elementary charge when expressed in coulombs and therefore fixed the value of the coulomb when expressed as a multiple of the fundamental charge.
where r is the distance between the point charges q and Q, and q and Q are the charges (not the absolute values of the charges—i.e., an electron would have a negative value of charge when placed in the formula). The following outline of proof states the derivation from the definition of electric potential energy and Coulomb's law to this formula.
In physical chemistry, the Faraday constant (symbol F, sometimes stylized as ℱ) is a physical constant defined as the quotient of the total electric charge (q) by the amount (n) of elementary charge carriers in any given sample of matter: F = q/n; it is expressed in units of coulombs per mole (C/mol).
The modern convention is to measure charge in coulombs, distance in meters, force in newtons, and energy in joules. Using coulombs requires using the Coulomb constant (k) in the equation. Rutherford used b as the turning point distance (called r min above) and R is the radius of the atom. The first term is the Coulomb repulsion used above.
In the SI system of units, the value of the elementary charge is exactly defined as = 1.602 176 634 × 10 −19 coulombs, or 160.2176634 zeptocoulombs (zC). [3] Since the 2019 revision of the SI , the seven SI base units are defined in terms of seven fundamental physical constants, of which the elementary charge is one.
Since ε 0, the vacuum permittivity, is not dimensionless, the coulomb is not dimensionally equivalent to M 1/2 L 3/2 T −1, unlike the statcoulomb. In fact, it is impossible to express the coulomb in terms of mass, length, and time alone. Consequently, a conversion equation like "1 C = n statC" is misleading: the units on the two sides are ...