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Charge density

  1. Mar 24, 2013 #1
    Hello,

    I am confused about how charge density is only related to the material of a conductor and not on any external factors.

    I don't see how the molecular weight, density, and avogadro's number dictate the charge density.

    Any help is appreciated, thanks
     
  2. jcsd
  3. Mar 24, 2013 #2

    Simon Bridge

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    That would be the mobile charge density - of course the actual charge distribution will be affected by external factors like the applied electric field.
    It is also possible to transfer charge from one thing to another.

    A lump of stuff is made up of atoms.
    The charges in atoms are protons and electrons.
    Not all the charges get to move about - atoms don't give up every electron just because we asked nicely. In general, protons like to hang about in the nucleus, and the nuclei like to hang out in some structure like a lattice or a molecule which restricts their movement. However, it is usually possible to pursuade each atom (or molecule) to let some of it's electrons move about. The number of electrons depends on the stuff.

    It follows that the amount of the different charges in a lump of stuff depends on the number of atoms it contains - and what sort of stuff it is.
    Numbers like molecular weight, density, and avogadro's number, are handy for working out how many atoms are in the lump of stuff.
     
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