Can high charges (like $1\times 10^{-3}$ coulomb) be acheived?

Question

How can we charge a metal electrode with large charges ? When i saw a video about measuring a charge using a visiostat on a balloon , the charge was 0.6 nano-coulomb. Is the charge of 1 coulomb unachievable?

Answer 1

It shouldn't be too hard with a Van de Graaff generator. Assuming a generator of radius to the order of a decimeter, we need to generate a potential of $\frac{q}{r} \tilde~ \frac{10^9}{0.1}\tilde~10^{10} V$ to get a charge of one coulomb. That would be rather hard, though if we want a microcoulomb, that can be arranged with a (Van de Graaff) generator capable of producing voltages in megavolts.

Once we have this charg on the generator, we can transfer it to the electrode via conduction (which will only transfer a fraction of it), or induction (which will induce an opposite and equal charge on the electrode)

So yes, charges in nanocoulomb/microcoulomb/millicoulomb aren't that hard to generate and collect. 1 Coulomb of charge -- not so much.

Note that it isn't too hard to have 1C of net charge in some given volume--the Earth has some net charge which is probably in coulombs. The issue comes when you have to concentrate it enough to be able to transfer it.

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I somehow forgot about capacitors. Capacitors can store a large amount of charge(till one kilocoulomb) though the net charge stored is zero. However, it is generally hard to transfer this high charge elsewhere without neutralizing it or pushing it into another capacitor.