- 176

- 0

http://img20.imageshack.us/img20/2964/physics16ri.th.png [Broken]

The working substance of a cyclic heat engine is 0.75kg of an ideal gas. The cycle consists of two isobaric processes and two isometric processes as shown in Fig. 12.21 (image above). What would be the efficiency of a Carnot engine operating with the same high-temperature and low-temperature reservoirs?

I don't know how to solve this problem. At first, I thought to simply use the ideal gas law as in,

PV/T = P

and to use that to go through each process, from 1 to 2, 2 to 3, and 3 to 4. I ended up with a temperature of 390K at point 4. The Carnot efficiency would then be 40% (1 - 390/650). However, that is wrong and that solution did not even use the mass of the ideal gas.

I then thought about using the mass to find the number of moles, PV=nRT. I found n = 0.80996 mol. But I don't know where to go from here...

The working substance of a cyclic heat engine is 0.75kg of an ideal gas. The cycle consists of two isobaric processes and two isometric processes as shown in Fig. 12.21 (image above). What would be the efficiency of a Carnot engine operating with the same high-temperature and low-temperature reservoirs?

I don't know how to solve this problem. At first, I thought to simply use the ideal gas law as in,

PV/T = P

_{2}V_{2}/T_{2}and to use that to go through each process, from 1 to 2, 2 to 3, and 3 to 4. I ended up with a temperature of 390K at point 4. The Carnot efficiency would then be 40% (1 - 390/650). However, that is wrong and that solution did not even use the mass of the ideal gas.

I then thought about using the mass to find the number of moles, PV=nRT. I found n = 0.80996 mol. But I don't know where to go from here...

Last edited by a moderator: