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Circuit Problems : Finding Current and Voltage

  1. Aug 4, 2011 #1
    1. The problem statement, all variables and given/known data
    The Circuit is given as shown in the figure
    http://img215.imageshack.us/img215/8361/circuitsl.jpg [Broken]



    find V,
    V, = ranging from 78v - 90v

    2. Relevant equations
    KVL
    E=E1+E2+E3...+En
    KCL
    I=I1=I2
    Ohms Law
    V=IR

    3. The attempt at a solution
    i used KVL
    72v-2000ohms(i)-0.5V,-V,=0
    then i have this equation
    72v=1.5V, +2000i (1)

    in the 2nd resistor with 3000ohms
    i derived the equation
    V,=(2I)(3000ohms)
    so V,=6000ohmsi (2)

    substitution in eq (2) and (1)

    i=0.007A

    then going back to eq (2)
    V,=42v <---- but this is not correct by looking at the range my prof gave me..
    so i think i missed something here or my whole idea is not correct..
    btw i dont really know if that 2i is in series with the resistor 3000ohms
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Aug 4, 2011 #2

    gneill

    User Avatar

    Staff: Mentor

    Where does the extra "-V," come from at the end? When I follow a KVL path around the first loop I go through the 72V source, the 2000Ω resistor, then the "0.5V," source and then back to the beginning via path AB.
     
  4. Aug 4, 2011 #3
    whew that solve my problem.. that "-V," is not included XD
     
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