boma

They teach Physics, Chemistry, Finance, Medical Sciences, etc. Couple of them teach at MIT, one at UNC-CH, several at Duke, couple more at Caltech. Many others at other Universities. I think these are reputable Universities. My native language is not English, so I may make English grammar mistakes, but I don't really care about grammar mistakes. If you can show me my error in physics it would be more appropriate in this topic. You know there people who start discussing personal features if they cannot tell anything on the subject. I hope you are not one of them. Because I am professor of Physics I tried to help you better understand Physics. I like the idea that students discuss Physics out of classroom and I will try to do a lot to help them. However, it seems a little bit strange that you are so negative about such participation. If you don't like my advise you are free not to follow it (as I mentioned above). However, that was advise from best intentions as you will never understand Physics if you accept everything you read in wikipedia without THINKING. I hope couple of people will accept my advise and will not educate themselves using that unreliable source of information. I promised I will not discuss wikipedia in that topic. Start another one. Send me an e-mail.

That has nothing to do with what I wrote about Physics. That was my advise (I may give advises, may not I?). As I mentioned I found TOO many errors in it and I don't recommend using it (I forbid to use it in my classes). From my point of view it will make you more harm (in terms of understanding Physics and other sciences) than good. Wikipedia is NOT peer (on PhD/MD/doctoral level)-reviewed source and the information is not reliable (it is true in about 60-70% cases -- my estimate, I might be wrong on the number). My friends also discourage their students from a use of wikipedia. And we are working in some of the best Universities in the US. I have not seen even single professor who said that there is no errors/problems with wikipedia in his/her area of expertise. However, the decision is yours. I am not going to discuss the quality of wikipedia in following posts. We may discuss it somewhere else if you wish. If you have questions about Physics I will be glad to answer them. Please send me e-mail.

Let me add couple of words. First, I would recommend never look at wikipedia. There are SO MANY errors in it, that one cannot distinguish what is true and what is not. I have checked randomly articles on Physics and Math. My estimate that about 30% have factual errors or simply wrong. I forbid my student to use it (or at least, if they use it I will not accept as an excuse if they make errors due to wikipedia). Second, in your first example the piston is indeed can transfer 100% heat into work. Nothing forbids that. What physicists mean by "efficiency cannot be more than 1-T2/T1" is no engine can transfer more than 1-T2/T1 (even in IDEAL model, with no friction, etc.) into work if the engine (actually its working body, like gas, etc) returns into initial state. If you push (very slowly to keep the pressure constant) your pistol back, you need to do some work (so, you prefer to lower the temperature inside of cylinder to decrease the pressure and therefore the work you need to push the piston back). That work should be subtracted from the work you received in the first part of the cycle. The first part work depends upon the high temperature (temperature of expansion), while the second (actually the third) part work depends upon the low temperature. So, the efficiency depends upon both. Third, it is not really matters if the process reversible or not. If the process is ideal and reversible, the engine may reach the 1-T2/T1 efficiency, while if the process is not reversible (like real-life processes), the efficiency cannot reach it in principle, it will be always lower. Fourth, everything above applies to ideal processes (no friction, etc.). If there are un-idealities (friction, heat loss, etc.) the efficiency will drop even for Carnot cycle (which has FOUR reversible steps). If you want to follow, just send me an e-mail, as I might not check the forum often.