Register to reply

PV diagram

by ally1h
Tags: diagram
Share this thread:
Jul26-08, 10:48 AM
P: 61
1. The problem statement, all variables and given/known data
A heat engine follows the cycle shown in the figure. a) How much net work is done by the engine in one cycle? b) what is the heat flow into the engine per cycle?


2. Relevant equations
W = -PΔV
ΔU = Q+W

3. The attempt at a solution
W = -PΔV
W = (-3.00 atm)(0.600 m^3)
W = -1.8 J

ΔU = Q+W
ΔU = 0, due to energy conservation
0 = Q+W
Q = W
Q = 1.8

Everything look okay? I wasn't so sure about part b....
Phys.Org News Partner Science news on
Experts defend operational earthquake forecasting, counter critiques
EU urged to convert TV frequencies to mobile broadband
Sierra Nevada freshwater runoff could drop 26 percent by 2100
Jul27-08, 03:58 AM
P: 208
Probably in part (b) the question asks for total heat added to the engine per one cycle, not the net heat gained (i.e. not [added]-[removed]). So, you should decide which part of the cycle corresponds to heating and then use

[tex]dQ = p\, dV + V\, dp[/tex]

to calculate the heat.
Jul27-08, 10:23 AM
P: 15
Quote Quote by ally1h View Post

3. The attempt at a solution
W = -PΔV
W = (-3.00 atm)(0.600 m^3)
W = -1.8 J
Your pressure needs to be converted into Pa to get the right units.

Register to reply

Related Discussions
Ray Diagram Introductory Physics Homework 3
Is the Loedel Diagram a Special Case of the Minkowski Spacetime Diagram? Special & General Relativity 11
Help with diagram Electrical Engineering 1
N-, V- and M-diagram Engineering, Comp Sci, & Technology Homework 6
Difference between Block diagram, Flowsheet and Flow diagram Engineering Systems & Design 1