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 formula for current I = Q / t, that would make the current a negative number. I don't reckon having read about negative currents though. So what's the explanation for how the negative sign dissappears and currents end up always being positive?

 

[Doc Al]

So what's the explanation for how the negative sign dissappears and currents end up always being positive?

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]

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

Sure.

 

[mosad655]

so let's 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]

so let's 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?

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 textbook 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]

In the textbook 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?

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]

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

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