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Electric Current

  1. Mar 4, 2009 #1
    1. The problem statement, all variables and given/known data

    A battery with emf, [tex]E[/tex], and internal resistance, r, is connected to a variable resistance, R, at points X and Y, as shown above on the left. Varying R changes, both the current I and the terminal voltage Vxy. The quantities I and Vxy are measured for several values of R and the data are plotted in a graph, as shown above the right.

    (a) Determine the emf of the battery.

    (b) Determine the internal resistance of the battery.

    (c) Determine the value of the Resistance that will produce a current I of 3 amperes.

    (d) Determine the maximum current that the batter can produce.

    2. Relevant equations


    3. The attempt at a solution

    I attempted to use Kirchhoff's loop rule. I'm not sure if I should be using it or not.

    (a) [tex]E[/tex] - Ir - R = 0
    [tex]E[/tex] = Ir + R

    (b) r = ([tex]E[/tex] - R)/I

    (c) V = IR
    R = V/I = 3V/3A = 1 ohms

    (d) I have no idea what to do.

  2. jcsd
  3. Mar 9, 2009 #2


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    Staff Emeritus
    Science Advisor
    Homework Helper

    Instead of "R", that term should be "I R", the voltage across resistor R.
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