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Homework Help: Circuit question with two batteries and resistors in pa

  1. Jan 13, 2017 #1
    1. The problem statement, all variables and given/known data


    Q: What is the power dissipated by R1?

    2. Relevant equations

    Ohm's law: V = IR
    Power: P = VI, I2R, V2/R
    Kirchoff's circuit and voltage laws

    3. The attempt at a solution

    I assumed the currents were I1 travelling rightwards from the top battery, I2 rightwards from the second battery, and came together to make I3 for the bottom branch. The bottom resistor pair I simplified to 10/7 Ohms. From here I assume I have to set up simultaneous equations to solve for I1.

    I used the equation for the bottom branch 1.5V - 10/7 * I3 = 0 to get I3 = 1.05A.

    I subbed this into the equation for the outer loop 1.5 - 3I1 - 10/7I3 = 0. However plugging 1.05A into this gave me 0 for I1...

    I feel like I'm way off the mark..
  2. jcsd
  3. Jan 13, 2017 #2
    Why would there be any current flowing in R1?
  4. Jan 14, 2017 #3


    User Avatar

    Staff: Mentor


    The current through R1 is determined by the PD across R1. So ask yourself: what is the P.D. across R1?
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