# Voltage reference point

1. Jul 17, 2012

### e44-72

Hello

I know that 5 volts in reference to ground (0 volts) is 5 volts as there is a potential differencce of 5 volts between 0 and 5 volts.

Does this mean 5 volts in reference to 2 volts would be 7 volts as there is a potential difference of 5 volts between 2 and 7 volts?

Thank you for any replies

2. Jul 17, 2012

### Staff: Mentor

What are "5 volts in reference to 2 volts"?
If you connect the "-"-side of a 5 volt power supply to a cable which has +2V (with your definition), the "+"-side will have +7V.

3. Jul 17, 2012

### phinds

If you are talking apples to apples (same ground reference in the same circuit) then 5 volts is 3 volts above 2 volts.

Your argument is exactly like saying that if I have 5 apples and you take away 2 of them, I should now have 7 because there is a difference of 5 between 2 and 7.

4. Jul 17, 2012

### CWatters

Voltage difference = Voltage on point A - Voltage on point B

Examples

Va Vb Difference
5 0 5
5 2 3
5 -2 7
-5 -3 -2

5. Jul 17, 2012

### michaelc187

potential diff is exactly that, -5 to -10

potential being the power-of-the-universe/desire to go from one difference (ie ground state) to another

difference.. being the "key word" in "potential difference" : excludes the ground/zero state

(as the ability of voltage/potential difference to perform is the same)