1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Voltage reference point

  1. Jul 17, 2012 #1

    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. jcsd
  3. Jul 17, 2012 #2


    User Avatar
    2017 Award

    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.
  4. Jul 17, 2012 #3


    User Avatar
    Gold Member

    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.
  5. Jul 17, 2012 #4


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

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


    Va Vb Difference
    5 0 5
    5 2 3
    5 -2 7
    -5 -3 -2
  6. Jul 17, 2012 #5
    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)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook