Electrons and currents

Currents are caused by moving charges and the measure of current is the number of coulombs passing by a point per second. IF a current is caused be electrons and each electron has a charge -1.6x10-19 Coulombs, then the number of electrons passing the point where the current, I, is measured is given by:

[I/1.6x10-19] electrons per second

We drop the - sign because we are interested in magnitude not direction. The - sign just means that the current is in the direction opposite the direction the electrons are going.