Simple Question Regarding Potential Differences

Other Hardware General Electronics
1

Hello all,

Sorry If I'm repeating an older post for my first on these forums, but over an hour of fruitless searching online has led me to asking a trivial question that I'm struggling to comprehend in order to ease my frustrations!

Consider a hypothetical circuit where the +ve port on a 10V DC power supply (A) connects ultimately to the same port on a 5V DC supply (B), rather than the supply A's own ground. As a current passes through a circuit only and ONLY when a potential difference is apparent, would one run through the circuit that I've just described? If so, could this circuit simply be redefined as one with a 5V operating voltage that's grounded at power supply B, considering that this is the difference between the power supply voltages?

Thanks in advance!!

2

If there's no connection back to A's v- there would no current flow.
Draw me a picture.

3

+10V -----------| R1 |------------- +5V

A B
0V 0V

Thanks for the swift reply. Sorry about the crude nature of the illustration (new guy is new :stuck_out_tongue_closed_eyes:).
Why would no current flow? Surely there's a potential difference of 5V between power supply A and power supply B?

4

If the 0V's are not connected, both supplies are isolated from each other. In this case, the resistor will "pull" the 10V and 5V together and you would measure 0V across the resistor.

5

could this circuit simply be redefined as one with a 5V operating voltage that's grounded at power supply B,

No.

considering that this is the difference between the power supply voltages?

It is not. This is because there is no common point.

If you measured with respect to the newly created +ve power rail then point A 0V would measure -10V and point B 0V would measure -5V.

If the two 0V lines were connected together then bang, or at least the resistor would have 5V across it and could, depending on the value, get hot.