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Homework Help: Find the efficiency of the heating

  1. Nov 10, 2008 #1
    1. The problem statement, all variables and given/known data
    A 2.5kW electric kettle takes 3 mins to raise the temperature of 1.2kg of water from a temperature of 20 degrees C to a temperature of 100 degress. The specific heat capacity of water is 4.2kJ/(kg K)

    2. Relevant equations
    So far I know that we're either using P=vit ot Q=mct
    How do i find:
    (a) enerygy output from 2.5kW heating element in a time of 3 mins, (b) efficiency of the heating.
  2. jcsd
  3. Nov 10, 2008 #2


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    Science Advisor
    Homework Helper

    Re: Heat

    A kw is 1000 J/second

    Calculate how much energy it took to heat the water and compare that with the answer from A
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