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Homework Help: EMF and internal resistance

  1. Nov 13, 2007 #1
    1. The problem statement, all variables and given/known data
    Hi, my first post here. :smile:
    Anyway im struggling with this homework, can someone help me out, show me what to do please.

    1)a cell can supply a current of 1.2A through two 2ohm resistors connected in parallel. When they are connected in series the value of the current is 0.4A. calculate the EMF and the internal resistance of the cell.

    2) A cell is joined in series with a resistance of 2ohms and a current of 0.25A flows through it. When a second resistance of 2ohms is connected in parallel with the first the current through the cell increases to 0.3A. What is the EMF, and what is the internal resistance of the cell?

    I really have no idea what to do, but i need to do this very quickly.

    Any help would be greatly appreciated
  2. jcsd
  3. Nov 14, 2007 #2
    EMF = 1.2 ( 1 Ohm + Ri )

    You write the equation.

    Two equations and two unknown variables ( Ri and EMF ). Solve !
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