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If we charge an object made of insulating material, the charges on it would leak to the medium as the time passes, due to the potential difference. I would like to know if there is a way to prevent leakage and conserve the charges on that object. I think, if we cover the object with an insulator which has higher volume resistivity than the insulator the object is made of, we would be able to make most of the charges stay in place. However, I am not sure if the charge flow is related with the electrical resistivity of materials. Is there a law which simply states that the charge flow could be prevented with good insulating although there is a potential difference? I know that the current in amperes is directly proportional to the conductivity of the material used in a circuit but would there be a way to create nearly no current at all?

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  • $\begingroup$ Do you mean that the insulator object has two disconnected surfaces and you place on one surface a charge, and on the other surface an opposite charge? $\endgroup$ – Sofia Jan 8 '15 at 2:32
  • $\begingroup$ @Sofia I meant that let's say we have a charged object which is made of insulating material. How can we prevent charges to leak away? Would covering the object with better insulators make charges to stay in the object since insulators stop charge flow? $\endgroup$ – user57144 Jan 8 '15 at 9:18
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When you charge an insulator, you typically put charge just on the outside. The insulator presumably needs to be connected to the "earth" in some way, and it is important that you use a good insulator for that mechanical connection.

You will find that the main leakage mechanism is usually moisture in the air. As long as the charged surface of the insulator is in contact with air, it will discharge (more quickly on humid days - this is why your clothes get "more static" in winter, since the humidity in the air tends to be lower). So if you can protect your insulator from moist air (maybe by putting it inside an evacuated chamber - or at least by surrounding it with another container and getting rid of the humidity) it will help a lot.

Sometimes you can help by including guard electrodes - these are electrodes that are designed to create zero electric field at some point along the conduction path, and which will thus prevent leakage.

More about charge loss on insulators can be found in this earlier answer

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  • $\begingroup$ In addition to these methods to prevent leakage, would covering our object with other insulators which prevents charges to pass on them help to make the charges stay in the object? $\endgroup$ – user57144 Jan 8 '15 at 9:14
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    $\begingroup$ If the insulator with which you cover your object is really good, the answer can be yes. But do look carefully at all leakage paths - if there are any, charge will find a way. $\endgroup$ – Floris Jan 8 '15 at 14:08
  • $\begingroup$ One last thing... Why the goodness of the insulators whom we use to cover is related to the leakage level? Is the rate of charges' loss inversely proportional to the the resistivity of the insulator? If yes, then why, which physics law states that? Thanks in advance. $\endgroup$ – user57144 Jan 8 '15 at 16:06
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    $\begingroup$ The current that flows depends on the electric field and the resistivity of the material. I assume you are familiar with Ohm's law - you can rewrite that in terms of electric field and bulk properties of the material. For a cylinder with area A, length $\ell$ you can write $V=IR$ or equivalently $\frac{E}{\ell} = \frac{I\rho\ell}{A}$ where $\rho$ is the resistivity. What I said above then follows. $\endgroup$ – Floris Jan 8 '15 at 18:05

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