[Physics] Is a Coulomb a count electrons or a measure of current

chargeelectric-currentelectricityelectrons

In "Is electricity instantaneous?" there were several answers that differentiate between 'electron flow' and 'current flow': electrons move slowly through a conductor, but the resulting current moves near the speed of light.

Given: 1 Coulomb = "6.3 billion electrons passing one point in a circuit in one second" [noted that this is not reflected in the SI definition which is 'the constant current needed to produce a (given) force in parallel conductors…']. Most sources I have read go with the "electrons/sec" definition, or "charge/sec" definition – including the tag here for electric-current. As a chemist I equate "charge" with "electrons" (not 'current flow').

Question: is a Coulomb based on a 'count' of slow electrons, or on the fast electric field generated by the moving electrons? [acknowledging that as a derived unit the Coulomb is really based on the Ampere – but this seems to be kind of circular reasoning at some level]

Best Answer

One Coulomb is defined as the charge transported by a current of 1 Ampere during 1 s. The Coulomb has nothing to do with the electric field generated by electrons.

As one electron has the negative charge of $1.602·10^{-19}C$, this means that 1 Coulomb has $6.24·10^{18}$ absolute values of electron, i.e. elementary charges. The Coulomb has thus a $6.24$ times a billion billion elementary charges