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Homework Help: Batteries in Parallel and series

  1. May 6, 2012 #1
    1. The problem statement, all variables and given/known data
    You are given two circuits with two batteries of emf "E" and internal resistance R1 each. Circuit A has the batteries connected in series with a resistor of resistance R2, and circuit B has the batteries connected in parallel to an equivalent resistor.
    Note that the symbol E should be entered in your answers as EMF.

    What is the power dissipated by the resistor of resistance R2 for circuit A, given that
    EMF=10 R1=300 ohms R2=5000 Ohms

    Calculate the power to two significant figures.

    2. Relevant equations

    3. The attempt at a solution

    well i used the second equation, and from previous question worked out my current in algebraic equation,
    I=2E/2R1+R2 so I= 2x10/2x300+5000 =1/280 R=5000+2x300= 5600


    P=(1/280)^2.5600= 0.07142857143

    how ever the correct answer to 2.s.f is 0.064
  2. jcsd
  3. May 6, 2012 #2


    User Avatar

    Staff: Mentor

    They're only looking for the power dissipated by R2. You've included all the resistance in your R.
  4. May 6, 2012 #3
    oh ok thanks, thread can be closed now.
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