Just knocked out my two biggest exams back to back. :dance: In fine shape too. All I have left is a speech tomorrow in a low-key class and I'm home for the holidays...

Feel quite ignorant right now :uhoh:

he meant 0 degrees kelvin the general law of gases, or ideal gases law? well whatever pressure * volume = R (0.82)*number of mol*temperature....

 

Rudy, you know why you forget everything when you go to sleep at 4 morning? because syou need 7.5 hours of sleep to record all that you learned during the day, besides studying a lot the day before the exam does not work, just pay attention during classes and you'll see that you're gonna remember everything

Exams are killing me right now. Been finishing this stupid essay today and I now need to spend the whole night revising for the exam tomorrow.

2 to go.

It's almost 5 in England and I gotta leave in like 3 hours. Scary.

Whoo crap, even though finals week for me is technically next week, two of my professors are leaving next week and thus holding their finals this Thursday and Friday. That's really bad, given how I also have two other non-final exams scheduled for Friday. Eep.

 

Actual finals week will be a cakewalk compared to the coming few days. And after Monday, I'm done with math class for the rest of my life, having completed all my requirements for that subject. It's the most up-in-the-air grade I have at the moment, as I've aced most quizzes yet flunked the midterm for some odd reason.

2 to go.

 

Best of luck. <3

this is the only one that I know.. :uhoh: err.. do you mean Charles' Law, Boyle's Law and Pressure Law :D:

Yes. The Combined gas laws - Charles' and Boyle's - you can split them up if you like, but it's just basic relationships. I prefer to use the formula PV/nT=PV/nT vs. PV=nRT even for room temperatures and normal pressure, as it's more flexible in the long run, and often we're faced with not normal conditions (auto engines climbing mountains, or rocket engines, etc.).

One thing to note - when you look at those charts (cycle diagrams) showing the various cycles, it's important to note that the expansion phase doesn't go the full length, and there's one point where energy is lost that could otherwise be doing useful work. This is because a piston can only travel as far as the crank allows, and unless there's a separate cylinder for expansion on a longer stroke, the gas still has some expansion to offer before being exhausted. Various other schemes work well - extra cylinders, exhaust turbines, etc.

I like the jet engine cycles the best, as they work on constant temperature and expanding volume, but not exactly something that one would put in a car (yet). There was someone at Texas A&M working on a low-pressure "low speed" brayton or Rankine cycle engine - a nifty thing that ran like a reverse compressor for refrigerants, and it looks promising, if the materials can hold up and it's not too noisy.

 

^ :shocked2:

I dont really understand about absolute temperature. Why do we need to use Kelvin instead of degree celsius?

Real gases are pretty close to ideal gases in their behavior, unless you get very near absolute zero (0 Kelvin). This is nice, since most of the equations work smoothly, and you can get a good estimate for mass balances, etc. in equations. Anyhow, it always amazed me how gas molecules could behave as so near to the theoretical ideal - sometimes nature really does work like it should!

Extra Credit (20 points) - Since high compression engines are closer to the theoretical maximum efficiency of an engine, what are three reasons why we don't use more high compression engines? What are some ways of overcoming these obstacles?

^ :confused: err.. i just finished my high school and unfortunately i forgot everything ive learnt :bigcry:

No exams till next week!!!! weeeeeeeeee:D:D:D:D:D

^ :confused: err.. i just finished my high school and unfortunately i forgot everything ive learnt :bigcry:

 

It's okay, the spies can't touch you ;)

It's okay' date=' the spies can't touch you :wink2:[/quote']

 

:laugh3: but they hide out in every corner! :P

^ :shocked2:

I dont really understand about absolute temperature. Why do we need to use Kelvin instead of degree celsius?

Lord Kelvin's scale was created as a way of measuring temperatures down to the coldest temperature possible, at which point all molecular motion stops. For the Combined Law equations, temperature is given in degrees Kelvin so the basic physics & mathematical framework for the equation works. All you really need to know is - just add 273.15 to celsius values to get the Kelvin temperature. If you want to know what it really means, take a few calculus courses, lean partial derivatives, and then take a course containing the physics of molecular motion.:P

just add 273.15 to celsius values to get the Kelvin temperature

 

yeah i know this :nice:

7 exams to go in this semester ...

=o

No exam today, surprisingly.

Just had my first exam of this semester today! One down, four to go! :nice:

Good luck everyone~ Ive been recently getting my exams back. I got 100% in maths, 98% in Science and 92% in english. Yay me~!

Wow, congratulations!

Great job!

just finished my exams, which most of you would appreciate. But not me, not me :cry:

just finished my exams, which most of you would appreciate. But not me, not me :cry:

 

Why? Didn't it go well?:\

I got 100% in maths' date=' 98% in Science and 92% in english.[/quote']

 

:shocked2: Good job, dude :thumbsup:

I got 100% in maths' date=' 98% in Science and 92% in english.[/quote']

 

:shocked2: Good job, dude :thumbsup: