# Heat engine (thermodynamics)

1. Oct 23, 2005

### huskydc

A heat engine has the three step cycle shown above. Starting from point A, 1 L (liter) of ideal gas expands in the isobaric (constant pressure) process A to B at P = 2 atm. B to C is isovolumetric process at V = 5 L, and C to A is an isothermal (constant temperature) compression at 300 K. (Note that the diagram is illustrating V vs P. This should make no difference in your calculations. )

I've already figured out that the pressure at point C is .4 atm

Find the heat (in J) exhausted in the process B to C if the internal energy of the gas U = 5.0J/K * T.

since its isovolumetric, W = 0, thus delta U = Q

so i did the following:

delta U = 1.5 n R (T(c) - T(b) )

I calculate T(b) by ideal gas law eqa..... then i get 1215.6 J....apparently that's incorrect, ...what am i supposed to do with the 5 J given????

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2. Oct 26, 2005

### huskydc

has anyone got any clues to this yet?

Last edited: Oct 27, 2005
3. Oct 27, 2005

### huskydc

i'm still stuck on this, i guess my question is what am i supposed to do with the U = 5 J that's given?