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Absolute Zero on celsius scale

  1. Apr 15, 2009 #1
    Hi ,
    Please help me to solve following problem.

    If 20 KJ are added to a carnot cycle at a temperature 100 degree Celsius and 14.6 KJ are rejected at 0 degree Celsius,determine the location of absolute zero on celsius scale?

    Ans -270.16 C

    Please tell me how to solve it

    Thanks in advance.
    Regards
    Arya
     
  2. jcsd
  3. Apr 15, 2009 #2

    Mapes

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    Hi Arya, welcome to PF. What do you know about the Carnot cycle relationships between extracted work, rejected heat, and the temperatures of the hot and cold reservoirs?
     
  4. Apr 16, 2009 #3
    Hi Mapes,
    In carnot cycle suppose Q1 is given as heat input and T1 is temperature of source,and
    Q2 is rejected heat at temperature T2(Temperature of sink),then (Q1/T1)=(Q2/T2) and if W is the work done by reversible cyclic heat engine then Q1=Q2+W.
    Now please tell me how to solve this problem
    regards
    Arya
     
  5. Apr 16, 2009 #4

    Matterwave

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    The Efficiency is defined as:

    [tex]E=\frac{Q_h-Q_c}{Q_h}[/tex]

    Qh is the heat extracted and Qc is the head expelled.

    Then, we can derive using basic thermodynamic laws that the efficiency of the Carnot Cycle is given by:

    [tex]E=1-\frac{T_c}{T_h}[/tex]

    Where Th is the temperature of the hot reservoir and Tc is the temperature of the cold reservoir. Can you figure it out from here?
     
  6. Apr 16, 2009 #5

    Mapes

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    Looks good. Now [itex]T_1[/itex] and [itex]T_2[/itex] are measured from the absolute zero of the system, which is a variable for this problem. So you can't just use 100°C and 0°C; rather, you need to reference these to the absolute zero variable. Then solve the equation for this variable.
     
  7. Apr 16, 2009 #6
    Thanks My Friend Mapes,
    I got it ,it solved my problem.Actually i was not taking absolute zero as a variable .Now i have solved it.Thanks
    regards
    Arya
     
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