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Find the Voltage in the following circuit diagram

  1. Sep 23, 2013 #1
    1. The problem statement, all variables and given/known data

    Find [itex]V_x[/itex] in the circuit.

    CFDeZ.jpg


    2. Relevant equations

    [itex]\displaystyle{\sum V_i=0}[/itex]



    3. The attempt at a solution

    I tried to add all of the voltages and label the 2 ohm res V1 and 1 ohm res V2.

    Then I did:

    [itex]V_x+V_1-15+V_2+2V_x=0[/itex]

    [itex]3V_x+V_1+V_2=15[/itex]

    but then I couldn't find any other equations that will aid me in solving this.
    I'm not really sure if I really need the V1 and V2.
    The circuit doesn't give you the current either, so I don't know why resistance would help.

    Thanks.
     
  2. jcsd
  3. Sep 23, 2013 #2

    berkeman

    User Avatar

    Staff: Mentor

    Welcome to the PF.

    Where did you come up with those equations? There is one current around that loop that generates the voltage drops and controls the voltage controlled current source. Could you please try writing the one equation for the loop again, and solving it?
     
  4. Sep 23, 2013 #3
    reply

    Is this right?

    [itex]i[/itex] is the current

    [itex]\begin{align*}
    2V_x+V_x+2i+i&=15\\
    3(5\cdot i)+2i+i&=15\\
    i&=\frac{15}{18}=\frac{5}{6}\;A
    \end{align*}[/itex]

    [itex]V=I\cdot R=\frac56 \cdot 5=\boxed{\dfrac{25}{6}\;V}[/itex]
     
  5. Sep 23, 2013 #4
    Also, current is the same throughout in a series circuit right/
     
  6. Sep 23, 2013 #5

    berkeman

    User Avatar

    Staff: Mentor

    The diamond source is a voltage controlled current source, right? Not a voltage...

    Correct.
     
  7. Sep 24, 2013 #6

    berkeman

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    Staff: Mentor

    Upon further review, and input from another Mentor, I may be wrong about the controlled source. It looks like a current source to me, but I could be wrong about that. It may be a voltage controlled voltage source (VCVS) instead. Sorry if I mislead you on this.
     
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