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Power and heaters

  1. Mar 2, 2009 #1
    1. The problem statement, all variables and given/known data
    A heater rated at 2000W operating at 250V is used on a supple of 230V. if the resistance of the heater will not be affected by temp, what is the power absorbed by the heater?


    2. Relevant equations
    i think that the only equation to use will be P=V^2/R


    3. The attempt at a solution
    because the resistance of the heater is its internal property, i would first compute for the resistance from: R=(230^2)/2000. afterwhich, i would compute the power absorbed by the heater through: V=250-230=20 -> P = (20^2)/R which will be computed from the previous equation. is this right?

    thanks!
     
  2. jcsd
  3. Mar 2, 2009 #2

    Redbelly98

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    Not quite. At 230 V, the power will be different than 2000 W.

    So, P is 2000W when V=?
     
  4. Mar 2, 2009 #3
    oh sorry. so, i think it shouldve been R=V^2/P and V=250V while P=2000W.

    so, the power when it operates at 230V is simply P= 230^2/R and the answer I would subtract from 2000W? is it right? thanks
     
  5. Mar 2, 2009 #4

    Redbelly98

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    Yes, correct up to this point.

    Uh, no. The problem statement asks for the power when V=230V. So just use the power you get from
    P= 230^2/R​
    ... and that's the final answer.
     
  6. Mar 2, 2009 #5
    lol, i misinterpreted the question. thanks, really!!!:D
     
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