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

Circuit problems

  1. Nov 28, 2005 #1

    I have this circuit (see attached file) and I'm trying to find the voltage between the two red points. I really don't know where to start.. could anyone help me out and get me started ?

    Thanks alot !
    - Edgar

    Attached Files:

  2. jcsd
  3. Nov 28, 2005 #2


    User Avatar
    Staff Emeritus

    Find the currents through all the branches.
  4. Nov 28, 2005 #3


    User Avatar

    Staff: Mentor

    Simplify the circuit first if possible, like look at R5 and R6 and think about ways to simplify the combination of them that won't affect the voltages that you are trying to calculate.

    Then just write a set of simultaneous equations that express how the currents flow through the different legs of the circuit, and solve for the two node voltages marked in red. Like, label the circuit with I1 going from the + (right) of the power supply, through the leg with R3, R4, R1. Label I2 as the current through the circuit leg through R2, R(combo), R7, R1. Then write equations for each node in the circuit, with the sum of all currents entering a node = 0. Solve away...
  5. Nov 28, 2005 #4
    Reply to berkeman

    thanks for your help, but that doesn't help much, you really didn't go in depth at all. i need more information
  6. Nov 28, 2005 #5
    yea... and? need more info!
  7. Nov 28, 2005 #6
    Edgar, I did it in grade 10 in Yugoslavia some time ago and I still remember it a bit; you have to simplify it=combine those rezistors; example from 4 make 2, from 2 make 1 etc. To that you should google parallel and series circuits and you will be surprised how simple and interesting it is. Very simple. But, you have to do a bit of reading. Good luck.
  8. Nov 28, 2005 #7


    User Avatar
    Gold Member

    Edgar White do you know of any DC network analysis techniques? For example using Mesh Analysis. This method involves solving a system of equations (simultaneous equations) which I'm sure you can solve right?

    It seems that your problem is not knowing the methods involved in circuit analysis. I'll give you a very good link to tutorial on some DC network analysis techniques. I do encourage you to read each of the discussed techniques and apply the one that (most easily) fits this situation.

    http://www.ibiblio.org/obp/electricCircuits/DC/DC_10.html [Broken]

    http://www.ibiblio.org/obp/electricCircuits/DC/DC_7.html [Broken]
    Last edited by a moderator: May 2, 2017
  9. Dec 28, 2005 #8
    Hi Edgar White :

    to find the voltage between the red points, use Thevinin's technique; by finding first the (Rth), then I short-circuit..
  10. Dec 28, 2005 #9
    Hi Edgar White :
    to find the voltage between the red points, use Thevinin's technique; by finding first the (Rth), then I short-circuit..
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Similar Threads for Circuit problems Date
Optimization Problem with an RC BP filter Sep 21, 2016
Power Supply Problems Apr 14, 2016
Problem in an ECG circuit Aug 14, 2015
Simple LDR Circuit problem... May 30, 2015
Discharging problem of a turn-off snubber circuit Dec 1, 2014