Subject: What Defines Voltage Levels?

I'm curious to know what property in an electrical circuit defines the 
voltage.  I've always taught that it was a function of the difference in the 
number of electrons between two points, that is, it was a function of the 
quantity of electrical charge.  However, current is measured in Coulombs per 
second and a Coulomb is an actually quantity of electrical charge (specifically 
6.25 x 10^18 electrons).  So it seems that a source capable of supplying a 
large current would posses a large electrical charge, and should have a 
corrosponding voltage level.  However, car batteries are only 12 volts but can 
source hundreds of amps.  Conversly a small ionizer may have a 7kV open circuit 
voltage (which would indicate a whole lot of charge) and yet it can only source 
a couple of mA, if that.  So if charge quantities aren't defining these voltage 
levels, what is?

Re: What Defines Voltage Levels?