# How to find the temperature of the cold reservoir?

1. Feb 18, 2016

### PhysicsstudentNOR

1. The problem statement, all variables and given/known data

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.

2. Relevant equations
The equation I used: e(carnot)=1-Tc/Th

3. The attempt at a solution
Tc=1-e(carnot)*Th
Tc= 1-0,60*650
Tc= -389 K

2. Feb 18, 2016

### Staff: Mentor

You didn't isolate Tc correctly.

3. Feb 18, 2016

### PhysicsstudentNOR

What's the right way to do it?

4. Feb 18, 2016

### Staff: Mentor

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 $e$.

5. Feb 18, 2016

Okey, tnx