Temperature in a Carnot heat engine

AI Thread Summary
The discussion revolves around calculating the temperature of the hot reservoir in a Carnot heat engine that lifts a 10 kg mass over 11 m in 95 cycles, exhausting 14 J of heat per cycle to a cold reservoir at 0°C. The initial calculations incorrectly assumed the heat exhausted was the total work output, leading to an unrealistic temperature of 1170°C. Clarification revealed that the heat exhausted (Qc) is separate from the heat input (Qh), allowing for the correct calculation of Qh as the sum of work (W) and heat exhausted. The correct temperature of the hot reservoir was determined to be 494 K, or 221°C. This resolution highlights the importance of accurately distinguishing between Qc and Qh in thermodynamic calculations.
EightBells
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Homework Statement


A Carnot heat engine takes 95 cycles to lift a 10 kg. mass a height of 11 m . The engine exhausts 14 J of heat per cycle to a cold reservoir at 0∘C.

What is the temperature of the hot reservoir?

Homework Equations


η=1-(Tc/Th)=W/Qh

The Attempt at a Solution


I've tried: (Energy to lift mass)/(number of cycles)=W, so (mgh)/95=((10kg)(9.8m/s^2)(11m))/95= W=11.35 J/cycle
∴ 1-(Tc/Th)=11.35/14, so Tc/Th=1-(11.35/14), Th=Tc/(1-(11.35/14))=273 K/(1-(11.35/14))=1440 K=1170°C

This is an incorrect answer, and logically it seems too high.

I also considered where the 14 J/cycle exhausted to the cold reservoir is the work out, but then I don't know how to calculate Qh so that I'd only have one variable in the equation listed under 'Relevant Equations'.
 
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The problem statement says 14 J is the heat exhausted to the cold reservoir, so it's ##Q_\text{C}##, not ##Q_\text{H}##. You calculated ##W## correctly. How do you get ##Q_\text{H}## from ##Q_\text{C}## and ##W##?
 
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vela said:
The problem statement says 14 J is the heat exhausted to the cold reservoir, so it's ##Q_\text{C}##, not ##Q_\text{H}##. You calculated ##W## correctly. How do you get ##Q_\text{H}## from ##Q_\text{C}## and ##W##?

Qh=W+Qc=11.35+14=25.35 J/cycle

Plug that into W/Qh=1-(Tc/Th) and Th=494 K=221°CThat's the correct answer, thanks so much!
 
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