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Homework Help: Help with power?

  1. May 20, 2009 #1
    a cell of emf 1.5V and internal resistance 0.5 ohms is connected to a 2.5 ohm resistor.

    ive calculated the current as 0.5A
    terminal pd as 1.25V
    and calculated the power delivered to the 2.5 ohm resistor.

    now i have to calculate the power wasted in the cell?

    ive got the equation Ie = I^2 + I^2r
    which is the power supplied by the cell = the power delivered to R + the power wasted in the cell.

    but im so confused. on rearranging it and subsituting the numbers in?

    can anyone shed any light on how i do this? and if so can you give me the equation and talk me through it please..

    thanks :)
  2. jcsd
  3. May 20, 2009 #2


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    Science Advisor

    How much power is dissipated in the internal resistance of the battery?

    A battery can only generate power but a resistor can "waste" it.
    Last edited: May 20, 2009
  4. May 20, 2009 #3
    ahh.. so i jus find out the amount of power delivered to the internal resistor and then thats my wasted power?
  5. May 20, 2009 #4


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    Science Advisor

    Yes, that's right.

    Asking it like that just turned a simple problem into a difficult one.
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