Lab 5 - Heat Engines and Cycles

A Simple Gas Cycle Of A Heat Engine

Above we have the graph of a simple gas cycle, where half the processes are isobaric (constant pressure) and the other half are isometric (constant volume). This is an ideal model, and i very unrealistic. 

Carnot Cycle

This cycle is a much more realistic cycle of a heat engine. It is used in gasoline burning engines (your car unless you drive a Tesla or a Diesel). I believe that some of the calculations of Work and Heat a inaccurate, so let me explain the faults for your better understanding:

From B->C and D->A the process is adiabatic, which means that there is not heat transfer, thus the Q for both of those processes should be 0 (zero) J. Thus indicating that the W=-dE. From there on out the calculations should fall into place

We used W=nRT*ln(V2/V1) for the Work of an isothermic process, hence from A->B and C->D.

W used W=((PiVi^y)(Vf^(1-y)-Vi^(1-y)))/(1-y), where y=gamma, in a adiabatic process.

The total work should be around 900J. Most the work is done in the power stroke from A->B.

ActivPhysics 8.7 - Heat Capacity

Problem 6:

In this model the pressure was held constant, as the temperature and volume changed.

Using the molar heat capacity formula we derived 20.75J/mole*K

Using two different temperatures which are fairly close to one another. 

Problem 7:

We did the same process as in problem 6, except that our change in temperature was the maximum possible, observing if there will be any difference than the previous problem.

Not much of a difference.. we calculated 20.78 J/mole*K

Problem 8:

Using a combination of formulas (1st law of thermodynamics, Internal energy, ideal gas law) and rearranging them, we calculated that the molar heat capacity is (5/2)R=20.785J/mole*K

This is very close to our calculations from problem 6&7.