Charge of an electron in Coulombs?

mosad655

Is it correct that the charge of an electron in Coulombs is

- 1,602 176 565(35) • 10^-19 C ?

By inserting this in the formular for current I = Q / t, that would make the current a negative number. I dont reckon having read about negative currents though. So what's the explaination for how the negative sign dissappears and currents end up always being positive?

Doc Al

Current is usually defined as flowing in the direction of positive charge carriers. (Historically, it wasn't anticipated that the charge carriers in a wire, for instance, were actually negatively charged.) So if electrons move to the right, the current is defined as moving to the left.

mosad655

but is it correct that the charge of an electron in Coulombs is - 1,602 176 565(35) • 10^-19 ?

Doc Al

Sure.

mosad655

so lets say.. 18 C would be then be 18 / (- 1,602 176 565(35) • 10^(-19)) electrons? That's a negative number, how is it possible to have a negative number of electons?

Doc Al

What's 18 C? Obviously not the charge on a bunch of electrons. Realize that if something ordinarily neutral is missing a number of electrons, that it will have a positive charge.

What problem are you trying to solve?

mosad655

In the text book that I have, it comes with this example:

A 5 amp current flows for an hour. The total charge that passes by in such case, is Q = I • t = 5 A • 3600 s = 18000 C or 18000 Coulombs. Now how many electrons is that?

Doc Al

Just divide by the magnitude of the electron charge. Don't get hung up with signs.

mosad655

So coulomb is not the unit for charge, but the unit for the magnitude of charge?

Doc Al

You can think of it that way. That's why the charge on the electron is a negative number of Coulombs.