help with Wheatstone Bridge

Discussion in 'Homework Help' started by terrakota, May 18, 2005.

  1. terrakota

    Thread Starter Well-Known Member

    Feb 8, 2005

    I'm trying to find the voltage betwen point A and B(the point that must be 0 to be the bridge balanced) I know i must use the voltage divider formula to find voltage from point A to ground ie. 3V, then i calculate the point B to ground voltage and is ie. 2v, to find the voltage betwen this 2 points i must substract 3v-2v = 1v.

    why i substract v1 from v2 and not v1+v2, or v1/v2? whats the theory why this 2 voltages must be substractedand not added or divided?

    thanks for any help
    and please excuse my poor english
  2. mozikluv

    AAC Fanatic!

    Jan 22, 2004

    if you have actually build the bridge and actually got the result and confirmed by the formula you can already deduced why you it's not add or divide.
  3. kshtron

    New Member

    May 29, 2005
    If you think of the two series paths from power to ground as two seperate circuits and calculate the voltage drop from the top of the grounded resitor (A and B) of each circuit to ground you will get different values in an unbalanced bridge. When both values are the same the bridge is balanced. Recall that voltage is defined as a difference of potential between two points. By subtracting the voltage between points A and B we establish the voltage between those points. By the way the sign only indicates direction of current flow. maybe this will help; I hope so.