(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A reversible engine contains 0.20 mol of ideal monatomic gas, initially at 600 K and confined to 2.0 L. The gas undergoes the following cycle:

Isothermal expansion to 4.0 L.

Isovolumic cooling to 300 K.

Isothermal compression to 2.0 L.

Isovolumic heating to 600 K.

Determine the engine's efficiency, defined as the ratio of the work done to only the heat absorbed during the cycle.

2. Relevant equations

efficiency, e = W/Q_h = (Q_h - Q_c)/Q_h = 1 - (Q_c/Q_h) where W is work, Q_h is heat energy (high), and Q_c is cool heat energy (low)

3. The attempt at a solution

in the problem leading to the question, i was asked to determine net work and net heat added during the cycle, there values are as follows:

net heat added during cycle: Q = 350 Joules

net work done during cycle: W = 350 Joules

now when i try and determine the efficiency i did this:

e = W/Q_h = (Q_h - Q_c)/Q_h = 1 - (Q_c/Q_h)

e = 350/600 = (600 - 300)/600 = 1 - (300/600), i used the 350/600 = 57.6% because the problem asked for the ratio of work and heat energy

i realized that 350/600 is not equivalent to the other ratios. since (600 - 300)/600 = 50% = 1 - (300/600) =/= 57.6%

which ratio am i supposed to use, the W/Q_h = 350/600 = 57.6% is incorrect? are my values correct for each variable?

thanks

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# Homework Help: Thermodynamics - engine efficiency

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