# Thermodynamics/ PV diagram

1. Nov 6, 2016

### Any Help

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

figure: http://www.chegg.com/homework-help/...ivides-p-v-diagram-regions-1-2-follo-q5905441

The dot in Figure (b) represents the initial state of a gas, and the isotherm through the dot divides the p-V diagram into regions 1 and 2. For the following processes, determine whether the change ΔEint in the internal energy of the gas is positive, negative, or zero.

(a) the gas moves up along the isotherm

(b) the gas moves down along the isotherm

(c) the gas moves to anywhere in region 1

(d) the gas moves to anywhere in region 2

1.ΔEint is positive
2.ΔEint is negative
3.ΔEint is zero

2. Relevant equations

curve of an isotherm is a hyperbola so as the hyperbola becomes closer to the center (0,0) at its inflection point the temperature decreases

deltaE internal= 3/2 nRdelta T means as temperature increases deltaE positive and Vise Versa

3. The attempt at a solution

when moving on isotherm the delta Einternal will be zero since Einternal depends on the change of temperature the a and b will be zero (a,b =3)

but while moving under the curve then we are getting a lesser temperature. the temperature decreases so delta E negative so c is negative (c= 2

similarly for moving above the curve then d is positive (d=1)

Last edited: Nov 6, 2016
2. Nov 6, 2016

### Staff: Mentor

Yes, provided in a and b you are dealing with an ideal gas.