Posted by Mark in Utah on Wednesday, May 01, 2002 at 3:23PM :
In Reply to: Re: It's not about how well they run... posted by Todd Wilson on Wednesday, May 01, 2002 at 1:21PM :
Electric potentials (voltages) are all relative. If the grounds of two circuits are connected with a conductive wire they will be at the same potential. The unconnected poles will have a potential equal to the difference of the separate circuits. In your scenario the potential difference would be 18 volts, -6v on one side of the common wire and +12v on the other side. The current flows when those other poles are connected. The problems happen when there is not a device in the second line that can handle the potential difference.
Mark.