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is it easier to negatively charge something than to positively charge it?

Discussion in 'Electronic Design' started by NG Neer, Jul 30, 2008.

  1. NG Neer

    NG Neer Guest

    imagine a balloon floating in the air, and you give it a negative
    charge. This pumps more electrons into it (or onto its surafce).
    Giving it a positive charge (in relation to its suroundings) is done
    by removing existing negative electrons. Once all the electrons are
    gone, how could you possibly give it more "positive" charge? Whereas
    you can put as many electrons onto you want, limited only by the
    voltage of your charging source (and dielectric breakdown).

    The analogy I'm thinking of is a sealed metal tank. as long as you
    have a strong enough compressor, you can pressurize the tank to
    whatever PSI you want (until it ruptures of course). But the opposite
    case, of sucking the air out to create a vacuum, you will never be
    able to create less than about -15 PSI (I'm talking Gauge pressure,
    not absolute pressure, which just like VOLTAGE is measured in relation
    to the surrounding "ground" conditions).

    Does electric charge work the same way?
     
  2. Tom Bruhns

    Tom Bruhns Guest

    Well, you could just as well give an object a positive charge by
    putting protons onto it, or positive ions. The difference is that the
    mass of a proton is much greater than -- about 1840 times -- the mass
    of an electron.

    You might also want to consider practical limits. A "pile" of
    electrons, or a "pile" of protons, will try mightily to get away from
    each other. I believe the capacitance of an electrically conducting
    sphere 1 meter radius in freespace is 111.3pF, more or less. So if
    you put a mere 1 coulomb of electrons on it (if you could actually do
    that), about 6*10^18 electrons, it will have a potential of nearly 9
    billion volts. Left as an exercise for the reader: what's the
    electrical field strength immediately outside such a sphere? What
    keeps the excess electrons on the sphere?
     
  3. Tim Williams

    Tim Williams Guest

    But protons don't like to hang around. Conservation of charge works, but
    physics being funny like it is, 13.6eV says those protons will grab up
    electrons, forming hydrogen which goes on its merry way, leaving the target
    electron-deficient. Depending on the material, some may chemically combine
    (I guess you could say a proton beam is the most acidic thing known to
    science, it's the ultimate Bronstead-Lowry proton donator), which you'd have
    to figure out in isolation of the charge. I suppose the way to tell would
    be to measure its mass extremely accurately, comparing equal charge (easy to
    measure) obtained by electron vs. proton bombardment. (Note that, at the
    charges we're talking, relativity will have a measurable effect. Assuming
    such apparatus that can actually measure these differences.)

    Tim
     
  4. CCD

    CCD Guest

    Well, as the study says, the +ve or -ve charge depends on the lack of
    the electrons or excess of the electrons as compared to protons. So,
    for creating +ve or -ve charge in an object, all u have to do is jus
    disturb the electron-proton balance. Pump extra electrons for -ve
    charged object, and suck out some electrons to create a positively
    charged object!!
     
  5. NG Neer

    NG Neer Guest

    Good answers, thanks everyone.
     
  6. Guest

    As has been pointed out earlier in this thread, you can't put much
    charge on a physical object before the mechanical forces generated by
    self-repulsion pull it apart. Thinking about protons as Bronstead-
    Lowry acids in this context is a pure waste of time.
     
  7. Tim Williams

    Tim Williams Guest

    Well it was an aside, hence the parenthesis. You're welcome not to read it
    (which is what parenthesis mean).

    Tim
     
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