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Mass dependency on charge

  1. Oct 16, 2009 #1
    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????
     
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  3. Oct 16, 2009 #2

    HallsofIvy

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    No, charge has no mass or weight.
     
  4. Oct 16, 2009 #3
    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
     
  5. Oct 17, 2009 #4
    hey bob!
    can u plz explain that how 100 C of electrons has a mass about 96 times less.
     
  6. Oct 17, 2009 #5
    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
     
  7. Oct 17, 2009 #6

    Vanadium 50

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    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?
     
  8. Oct 17, 2009 #7
    [STRIKE][/STRIKE]
    Hi Vanadium50-
    This is calculating the rest mass of each sphere in isolation. [STRIKE][STRIKE][STRIKE]When the two spheres are brought close together, the Coulomb force is about [STRIKE]8[/STRIKE]9 billion (9 x 109) Newtons at 100 meters, so perhaps a kilometer might be better[/STRIKE][/STRIKE][/STRIKE].
    [STRIKE]Because the positive sphere is missing 100 Coulombs of electrons, and the negative one has 100 Coulombs of extra electrons,[/STRIKE] the more negatively charged sphere has more mass.
    Bob S
     
    Last edited: Oct 17, 2009
  9. Oct 17, 2009 #8

    Vanadium 50

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    Bob, I think it's best for the OP to tell us what he is trying to calculate rather than guessing.
     
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