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Homework Help: Thevenin circuit Max power across Load resistor

  1. Sep 17, 2012 #1
    1. The problem statement, all variables and given/known data

    One Thevenin theorem result is that the maximum power across the load resistor in the equivalent circuit (and therefore the real circuit) occurs when RL = Rth. Start with the result that the power dissipated by the load resistor is I2RL and prove this result.

    2. Relevant equations

    3. The attempt at a solution

    I have really no idea where to begin with this question. I do understand what a Thevenin circuit is, and where i would place a load resistor. Im just looking for some direction as to where to start, or for someone to point me towards what i should be thinking about and working with to get towards an answer.

    any help or thoughts would be greatly appreciated.
  2. jcsd
  3. Sep 17, 2012 #2


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    Staff: Mentor

    Draw the circuit. Obtain an expression for the power in the load in terms of the given components, yielding the power as a function of RL: P(RL) = ....

    Find the maximum w.r.t. RL.
  4. Sep 18, 2012 #3
    I think ive figured it out. I can solve for I, input that into


    Since im trying to max. power disipated by RL i can take the first derivative and set it equal to zero.

    does this sound incorrect to anyone?
  5. Sep 18, 2012 #4


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    Staff: Mentor

    Nope. Sounds like a good plan.
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