# Difference between charge, specific charge, relative charge and elimentary charge?

1. Sep 19, 2010

### physics369

Hi,

Sorry if I have posted this in the wrong place. I'm having trouble understanding the difference between these four measurements of charge. Specifically whether the -/+ sign is important and what the unit is:

For example,

The charge of an electron is -1.602176487(40)×10^-19 coulombs, right?

The relative charge of an electron is -1, right? Because to get the relative charge you divide by the charge of an electron and, because it's negative, you add a - sign, right? Has this got a unit?

The elementary charge of an electron is the same as the charge, but because it's absolutely charge, the signs (-/+) are irrelevant, right? Is this also measured in coulombs?

For specific charge, you use the elementary charge and divide that by the mass, right? So for an electron it would be 1.60x10^-19 / 9.11 x 10-31. giving you 1.76x10^11 Ckg-1, right?

Any help/guidance would be much appreciated. :)

2. Sep 20, 2010

### daschaich

Re: Difference between charge, specific charge, relative charge and elimentary charge

I wouldn't get hung up on the terminology (some of which is new to me). The important thing is to specify the units with any numerical value. Units are present for your first and fourth examples. For the second and third, I would say that the electron's electric charge is -1 in units of the proton's electric charge, or +1 in units of the electron's electric charge.