Coulomb

A Coulomb [ Kulo ː ] ( unit symbol C) is the SI derived unit of electric charge (symbol Q or q). It is named after the French physicist Charles Augustin de Coulomb.

A coulomb is defined as the electric charge is transferred within one second by the cross section of a wire, in which an electric current of one ampere flows of:

Comparison with the electrical elementary charge

An occurring in nature electric charge Q can only ever be an integer multiple of the elementary charge e. The units of the SI system of units, however, were set arbitrarily. Therefore, it is not guaranteed that a coulomb is also an integral multiple of the elementary charge.

The base unit second is defined as an exact multiple of a certain natural period. Similarly, one could define by specifying a whole number of elementary charges in principle, the Coulomb and return the base unit ampere it. Such a modification of the system of units is not currently planned.

The elementary electric charge can ( among other things) the represented von Klitzing constant RK as a combination of the Josephson constant KJ and:

For these two constants in 1990, so-called conventional values ​​were determined. Due to the finite precision of the two values ​​is then obtained, although the statement that a Coulomb 6,241,509,629,152,650,000 elementary charges omitted ( an integer). However, this must not be considered as evidence of an actual integer.

Historical

The Coulomb has replaced the electrostatic CGS unit ESU or Franklin ( Fri):

The speed of light