Why doesn't current flow between battery terminals of opposite polarity?

[Ahsan Khan]

Hi all,I discussed this question yesterday but didn't get a satisfactory answer.Why do no charge flows when the +ve terminal of one battery is connected to the -ve terminal of another battery.Please don't just say that my circuit is incomplete or open.In textbooks i read when two bodies placed a distance apart are placed on an insulated stand and they given opposite charge and when a wire is mad e to join them then electron begin to flow from -ve body to +ve body,though sudden though not in a flow but it do

 

[gneill]

Charge can flow until the the potential difference goes to zero between the two terminals. If electrons flow from the -v terminal of one battery to the +v terminal of the other, that creates a net buildup of positive charge on the battery that they left, and buildup of negative charge on the battery that they go to (by conservation of charge). That establishes a net potential difference between the batteries as a whole that will rise until it negates any difference in potential between the two terminals. No further current can flow then.

This will happen very rapidly and involves very small mounts of charge. You can an idea of how much charge by modelling the two batteries as isolated spheres. How much charge needs to be transferred in order to establish a few volts of potential difference? I'd estimate less than a nanocoulomb, or about a millisecond of one microamp of current. Then it's all over.