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Amount of kWh used to heat water

  1. Apr 10, 2013 #1
    1. The problem statement, all variables and given/known data

    How much kWh is beeing used to heat 285 liters of water in a water heater from:
    1. + 5 °C to + 75 °C
    2. + 20 °C to + 75 °C

    2. Relevant equations

    Found this equation:

    kWh = (Q*CJ*∆t)/T

    3. The attempt at a solution

    Q = liter = 285
    Cj = heat capacity = 4,18
    ∆t = 70 for 1. And 55 for 2.
    T = is the time, but I'm not sure what to use here, so I used 3600.

    So my answer was:
    1. 23,2 kWh
    2. 18,2 kWh

    I have no clue if this is right or wrong because of the variable T. What is correct here?
     
  2. jcsd
  3. Apr 10, 2013 #2

    rock.freak667

    User Avatar
    Homework Helper

    kWh is a unit of energy, so just calculate the energy using QC∆t, and then convert.

    1 kWh = 1 kW * 1 hr = 1000 J/s * 3600 s = 3,600,000 J

    So 1 J is?

    Then just convert!
     
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