1. Not finding help here? Sign up for a free 30min 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!

DC circuit, find current and potential

  1. Oct 8, 2011 #1
    View attachment 39765

    a) Calculate the current through the 5Ω resistance. Use '+' sign for the current directed from right to left, and '-' sign if the current flows from left to right.

    b) The magnitude of the potential at 'a' is?


    Please help me with the two questions above. I have tried to used the Kirchoff's law. but it doesnt seem to work for me. Thank you in advance!

    (clicK on the picture to view the circuit)
     
    Last edited by a moderator: Oct 9, 2011
  2. jcsd
  3. Oct 8, 2011 #2

    vk6kro

    User Avatar
    Science Advisor

    You would really have to show your attempt at using Kirchoff's Laws, including the equations and a diagram showing the currents and voltages referred to in the equations.

    Without that, we would have to just do the problem for you and that is against the rules here and also wouldn't do you any good.
     
  4. Oct 8, 2011 #3
    here are my attempts:

    First i made 4 different loops. each one of them looking like this by using Kirchoff's current law:

    A) 19-9I3-6I4+7-5I1=0
    B) 7-5I1-16I2=0
    C) 7-5I1+19-9I3-6I4=0
    D) 19-9I3-6I4+16I2=0

    But now I feel like im stuck I dont know what to do. I dont even know if im on the right track or not. I need help
     
  5. Oct 8, 2011 #4

    vk6kro

    User Avatar
    Science Advisor

    You can combine the 9 ohm and 6 ohm resistors to get 15 ohms. This will cut down on the typing a bit.

    Try using two currents. One going right from point "a" and one going down from point "a". The one through the 7V battery can be derived from these two currents.

    Modify the first diagram to show the new currents and the polarities of the voltages across the resistors.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook