How to find the temperature of the cold reservoir?

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SUMMARY

The discussion focuses on calculating the cold reservoir temperatures for two Carnot engines with efficiencies of 0.60 and 0.80, respectively, using a hot reservoir temperature of 650 K. The correct formula for determining the cold reservoir temperature (Tc) is derived from the Carnot efficiency equation: e = 1 - Tc/Th. The accurate calculation for engine A yields Tc = 1 - 0.60 * 650, resulting in an incorrect negative temperature, indicating a miscalculation. The correct approach involves rearranging the equation to isolate Tc properly.

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Homework Statement



Carnot engine A has an efficiency of 0.60, and Carnot engine B has an efficiency of 0.80. Both engines utilize the same hot reservoir, which has a temperature of 650 K and delivers 1200 J of heat to each
engine. Find the magnitude of the work produced by each engine and the temperatures of the cold reservoirs that they use.

Homework Equations


The equation I used: e(carnot)=1-Tc/Th

The Attempt at a Solution


Tc=1-e(carnot)*Th
Tc= 1-0,60*650
Tc= -389 K
 
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PhysicsstudentNOR said:
The equation I used: e(carnot)=1-Tc/Th

The Attempt at a Solution


Tc=1-e(carnot)*Th
You didn't isolate Tc correctly.
 
DrClaude said:
You didn't isolate Tc correctly.

What's the right way to do it?
 
The equation
$$
e = 1 - \frac{T_c}{T_h}
$$
is correct, but that doesn't mean that
$$
T_c = 1 - e T_h
$$
Start by moving the 1 to the same side as ##e##.
 
DrClaude said:
The equation
$$
e = 1 - \frac{T_c}{T_h}
$$
is correct, but that doesn't mean that
$$
T_c = 1 - e T_h
$$
Start by moving the 1 to the same side as ##e##.
Okey, tnx
 

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