# Calculating induced charge

Let's say I have a battery with V volts. A conductive material (Material A) is connected only to the battery's positive terminal. Material A is then connected to a second conductive material (Material B) that is not connected to anything. After Material A and Material B touch, they will then be separated. How do I calculate the charge on Material B after the two were separated?

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Sounds like homework. What don't you understand? –  Brian Carlton Jul 24 '12 at 19:04
actually I want to make something, and for that I need to charge a few metal balls with 2mm radius... and I thought that this is the best way to charge them... may be I should have asked how to charge a 2mm radius balls to a certain charge –  Someonation Jul 24 '12 at 19:10
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## 1 Answer

Charge (Q) is the product of current (I) and time (t).

When you connect something to one side of a battery only, no current will flow, and no charge will be transferred, except for extremely tiny amounts of charge when you consider your conductive parts as plates of capacitors.

There are some experiments with high voltage that work a bit like what you mention in your question. At high voltages, charge transfer can even be observed in the form of tiny sparks.

However, without knowing how big your setup is, and what (stray) capacitance to use, it is nearly impossible to calculate anything.

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but current accures when you have a difference in potentials, and the potantial of the condactive metirial that is connected to the battery is higher that the potential of the condactive metirial that is not connected to anything –  Someonation Jul 24 '12 at 19:16
The part that you connect to the battery will only have a known higher or lower potential if you have connected it to something else before. Once you connect it to the battery, the amount of charge transferred depends on the capacitance it forms to other things around it. Even if everything happens in air, and we thus know the dielectric, we still have to know the geometry of everything else in the setup. –  zebonaut Jul 24 '12 at 19:35
by geometry you mean the volume of each metirial? –  Someonation Jul 24 '12 at 19:36
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