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Finding the current

  1. Jun 1, 2016 #1
    1. The problem statement, all variables and given/known data
    There is a circuit which is shown in the picture. ##R_1=10 Ω;## ##R_2=10 Ω;## ##R_3=30 Ω##.
    I need to find what ampermeter is showing.
    123.png

    2. Relevant equations
    U=IR

    3. The attempt at a solution
    1234.png
    I am trying to use kirchhoff rules here.

    ##I_1=I_2+I_3##
    ##I_1R_1+I_3R_3=80##
    ##I_2R_2=I_3R_3##

    I get that ##I_3=1.14A##. Is this correct?
     
  2. jcsd
  3. Jun 1, 2016 #2
    Assuming C & D are open as shown, I2 should be 0.
     
  4. Jun 1, 2016 #3
    But how do I know whether there is voltage between C and D? It is not stated in the problem. In fact, the next question of this problem asks to find the voltage between C & D.
     
  5. Jun 1, 2016 #4

    NascentOxygen

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    Staff: Mentor

    There will be a voltage between C and D, even though I2 = 0.
     
  6. Jun 3, 2016 #5

    CWatters

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    Science Advisor
    Homework Helper

    That last line isn't correct. The voltage across R2 and R3 are not the same.

    There is nothing connected to C and D so no current flows into or out of C and D. So I2 = 0. Think what that means for I1 and I3.
     
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