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!

Circuit with Four Resistors and Two Switches

  1. Mar 2, 2016 #1
    1. The problem statement, all variables and given/known data
    Four resistors connected to a battery are shown in the figure (at bottom). The switch S2 is closed and switch S2 is left open. What is the magnitude of the potential difference Vcd

    2. Relevant equations
    Rp= Σ(1/Ri)-1

    Rs = ∑Ri

    V = IR
    3. The attempt at a solution
    Seeing as c and d aren't directly connected since S2 is open, I attempted to find the total resistance using the two resistance equations above and from that find the total current. After that, I divided the total current by two since the total resistance on both sides are the same, and multiplied that by the total of the top resistance. Next I added the current multiplied by the bottom left resistor and subtracted the current multiplied by the bottom right resistor, but I don't think this is correct.
    upload_2016-3-2_18-18-20.png
     
    Last edited: Mar 2, 2016
  2. jcsd
  3. Mar 2, 2016 #2

    gneill

    User Avatar

    Staff: Mentor

    Hi Jake Russell, Welcome to Physics Forums!

    The mage that you tried to attach isn't viewable. Can you upload it again?
     
  4. Mar 2, 2016 #3
    I ended up figuring out this question (I wasn't starting at a and not c), but I have another one. How would I find the current through the second switch when it is closed?
     
  5. Mar 2, 2016 #4

    gneill

    User Avatar

    Staff: Mentor

    With switch S2 closed can you find the potential at node cd? (Since S2 joins c and d together, they become a single node).

    Knowing the potentials at a,b, and c, can you write a KCL equation at location c?
     
  6. Mar 2, 2016 #5

    CWatters

    User Avatar
    Science Advisor
    Homework Helper

    Work out the voltage drop across each resistor (easy) then calculate the current in each resistor and mark it on the diagram. Apply KCL at either node c or d.

    Edit: cross posted with gneill.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Circuit with Four Resistors and Two Switches
Loading...