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Three Carnot engines operate in series between a heat source at a temperature T_{1}  and a heat sink at temperature T_{4} (see figure). There are two other reservoirs at temperature T_{2} and T_{3} , as shown, with T_{1}>T_{2}>T_{3}>T_{4}. The three engines are equally efficient if:

  • Option 1)

  • Option 2)

  • Option 3)

  • Option 4)

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best_answer

 

Efficiency of a carnot cycle -

\eta =\frac{W}{Q_{1}}=1-\frac{T_{2}}{T_{1}}

T_{1}\, and\, T_{2}  are in kelvin
 

- wherein

T_{1}= Source temperature

T_{2}= Sink Temperature

\left ( T_{1} > T_{2}\right )

\varepsilon _{1}=1-\frac{T_{2}}{T_{1}}\\\\\varepsilon _{2}=1-\frac{T_{3}}{T_{2}}\\\\\varepsilon _{3}=1-\frac{T_{4}}{T_{3}}\\\\\varepsilon _{1}=\varepsilon _{2}=\varepsilon _{3}

 

\Rightarrow 1-\frac{T_{2}}{T_{1}}= 1- \frac{T_{3}}{T_{2}}=1-\frac{T_{4}}{T_{3}}

\frac{T_{2}}{T_{1}}=\frac{T_{3}}{T_{2}}=\frac{T_{4}}{T_{3}} \\\\\Rightarrow \frac{T_{2}}{T_{1}}=\frac{T_{3}}{T_{2}}\\\\\Rightarrow T_{2}=\; \sqrt{T_{1}T_{3}}--------(1)\\\\SIMILARLY\\\\ \: \: T_{3}=\sqrt{T_{2}T_{4}}-----(2)PUT \: IN \: (1)\\\\T_{2}=\sqrt{T_{1}T_{3}}\\\\T_{2=\sqrt{T_{1}\sqrt{T_{2}T_{4}}}}\\\\T_{2}=T_{1}^{\frac{2}{3}}T_{4}^{\frac{1}{3}}

 

 

 

 


Option 1)

Option 2)

Option 3)

Option 4)

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