# Mass dependency on charge

1. Oct 16, 2009

### astro2cosmos

it may bit a fuzzy problem but still i have this confusion i.e suppose i have two sphere of same radius & all physical & material properties are same but 1st sphere has a charge of 0.0000001C & another have 100C. and if i measure the weight of both then which will be heavier????

2. Oct 16, 2009

### HallsofIvy

No, charge has no mass or weight.

3. Oct 16, 2009

### Bob S

hello Astro-
One gram molecular weight (GMW) of electrons has a mass of 0.0005446 grams. 100 C of electrons has a mass about 96 times less. So a sphere with +100 C of charge will have a lesser mass than an "identical" sphere with -100C, because electrons have a negative charge.

"identical" means the same number of protons and neutrons.
Bob S

4. Oct 17, 2009

### astro2cosmos

hey bob!
can u plz explain that how 100 C of electrons has a mass about 96 times less.

5. Oct 17, 2009

### Bob S

Sure. A GMW (gram molecular weight) of protons has a mass of 1 gram, and contains 6,02 x 1023 protons (approximately). The mass of an electron has a mass 1836 times less (remember hydrogen atom). The charge on an electron is 1.6 x 10-19 Coulomb, so a Coulomb contains 6.25 x 1018 electrons. So a GMW of electrons contains 96,320 Coulombs of electrons.
Bob S

6. Oct 17, 2009

Staff Emeritus
I think you'll need to supply more information about what exactly you're trying to calculate here. Is it the mass of electrons? (And remember, if I have a positive charge, I'm removing electrons). Is it the relativistic mass equivalent of the potential energy from assembling this charge configuration? Is it something else?

7. Oct 17, 2009

### Bob S

[STRIKE][/STRIKE]