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Homework Help: Alter resistance for max power dissipation?

  1. Dec 2, 2015 #1
    1. The problem
    Given a circuit with a 30V source and five resistors. The circuit can be drawn as two boxes. Resistor 1 (R1 = 300ohm) is in series with the source. R2 (300ohm) in the middle of the two boxes, and the remaining resistors (550 ohm) in series at the other side of the box.

    The problem states: Find the power dissipated from R2 and given the possibility to adjust R2 find the max power dissipated.
    2. The attempt at a solution
    have found the power dissipated from R2, however, how can i "alter" the value of R2 (from 300 to something else) to reach a max value for power dissipated? Is the question badly written or is there a way to find a max allowed power dissipation.
    Last edited by a moderator: Dec 2, 2015
  2. jcsd
  3. Dec 2, 2015 #2


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    Homework Helper
    Gold Member

    What do you mean by boxes? It would be helpful if you drew the circuit diagram.
  4. Dec 2, 2015 #3


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    Staff: Mentor

    Hi Einar. :welcome:

    Perform your calculations using "R2" as the value of that resistor, to determine its power (its voltage x its current) as an algebraic expression in terms of that pronumeral, R2.

    Then sketch the equation and use calculus or otherwise to determine the value of R2 for which its power expression peaks.
  5. Dec 3, 2015 #4
    Ok thanks I think i got it.
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