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Homework Help: Phys Chem Heating water with electric current

  1. Sep 24, 2013 #1
    1. The problem statement, all variables and given/known data
    86.9g of liquid water at 304K is heated by 1.75A passing through 24.7Ω for 104s what is the final temp

    2. Relevant equations
    its been a while since i did physics so bear with me if i get something mixed up here
    q=mCs,pΔT q=ItΔψ ψ=pot dif so isnt that just V from v=IR?

    also i believe the q=ItΔψ results in units as AVs if A=Cs-1 then we would get CV which is = to 1J???? long shot but maybe im correct

    3. The attempt at a solution

    assuming the above is true i want to say that Tf=[(I2tR)/(Cs,pm)]+Ti

    plugging in a bunch of numbers and if those units worked out how i think i get 325.65K

    Does this seem legit?
  2. jcsd
  3. Sep 24, 2013 #2


    User Avatar

    Staff: Mentor

    Looks good. It's handy to remember a few relationships for electric power when resistors are involved: P= VI, P = V2/R, and P = I2R.

    Sure. But since you're not given the potential difference (Voltage) across the resistor but your are given the current, you can use the current-version of the power expression. Then

    ##q = I^2R\:Δt~~~~~~~~~~~##where Δt is the elapsed time that the current flows.

    Sure. Not only that, but your results looks good :smile:
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