Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Circuit: Potential Difference

  1. Apr 7, 2010 #1
    1. The problem statement, all variables and given/known data
    For the circuit in the figure below, V = 3.56 V and R = 2.04 Ω. Find the potential difference between points a and b.

    This is the link to the figure: http://i749.photobucket.com/albums/xx137/abcdmichelle/physics/26-62alt1.gif

    2. Relevant equations

    3. The attempt at a solution
    So I needed to find the current passing through R.
    I said that the resistor at the top left had current I, the resistor at the top right was I(2), the resistor at the bottom left was I, the resistor at the bottom right was I(2), and the resistor R in the middle had a current of I(3).
    I applied the junction rule and the loop rule to the left hand side loop, and found the current to be:

    Current I(3)=0.76

    So then to find the potential difference I did:
    V= -(0.76)(2.04)-3.56

    This is wrong, I'm not sure if I did anything right here!
    Please help!
    Last edited: Apr 7, 2010
  2. jcsd
  3. Apr 7, 2010 #2


    User Avatar
    Science Advisor
    Homework Helper

    welcome to pf!

    hi abcdmichelle! welcome to pf! :smile:

    (try using the X2 tag just above the Reply box :wink:)
    no, you've cancelled the potential differences for the two 1Ω resistors … the current is flowing the "same" way through them, so they will add

    also, you normally need two loop-equations to solve a two-loop problem (though in this case you can get a relationship between I1 and I2 from symmetry) :wink:

    (btw, are the 2V batteries 2 volts, or 2 times 3.56 V ? :confused:)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook