# Heat on PV Graphs

1. Dec 1, 2005

### Dooh

How do i calculate Q transferred in a PV graph (Pressure / Volume)? More specifcally, when it is a slope. All that was given is pressure and volume from the graph.

Also, in an isochoric process, how would one go about finding Q? I spent so much time on thermodynamics yet i still dont know how to find it.

2. Dec 1, 2005

### mezarashi

Generally, there is no direct way to do so. You have to consider that

$$U = Q - W$$

The internal energy is dependant on temperature. Work is always a function of pressure and change in volume. There are interesting relationships for example if the process is adiabatic, so it depends on the situation. A combination of the ideal gas equation, adiabatic equation or use of saturation/compressed water/refrigerant tables may be needed depending on your problem.