# 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 NeerGuest

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 BruhnsGuest

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 WilliamsGuest

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. ### CCDGuest

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!!

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