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Proof , newtond law of cooling

  1. Mar 15, 2007 #1
    Ok hi guys,
    recently i was doing a practical on thermodynamics. Then i came across of a question which was to comment on the assumption that the rate of heat loss for 2 different liquids , placed in identical calorimetry copper cups was the same.( the 2 liquids started off at the same temperature ( the liquids were oil and water)).

    Ok my reasoning for the rate of heat loss being the same was that the copper cup,can only have a loss in energy at a fixed amount of power as the dimensions of the cup are kept constant. Please correct me if i am wrong.

    Then i also commented on newtons law of cooling( rate of change of temperature is proportional to the difference in temperature between the objects temperature and the ambient temperature) If it were to be written in a equation,it would be the (rate of change in temperature = -k(T - Troom) . Okay the k here is a constant which is different for every object.My reasoning is that to bring down the temperature of 2 different objects by a kelvin would require different amounts of energy as the the specific heat capacity of every object is unique. Furthermore the rate of energy loss is the same,hence 2 different objects would not have the same k value.Asthey would require different amounts of time to cool down. Please comment on these satements
  2. jcsd
  3. Mar 15, 2007 #2


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    Staff: Mentor

    Assuming I understand your reasoning, you are correct: the rate of heat transfer for any given temperature is the same, but since the specific heats are different, the rates of temperature change are different.
  4. Mar 15, 2007 #3
    Thank you!
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