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Mar
30
comment Why are magnetic lines of force invisible?
This is an interesting question. Too bad it was never answered. Some species of birds can see magnetic fields, after all.
Mar
29
comment Why is AC more “dangerous” than DC?
I think he means that, since he clearly describes it in his question
Mar
27
revised What is the meaning of $h_L - h_H$ for a heat engine?
added 87 characters in body
Mar
27
revised What is the meaning of $h_L - h_H$ for a heat engine?
added 104 characters in body
Mar
27
comment What is the meaning of $h_L - h_H$ for a heat engine?
Also, I know I tag this as homework (as is the practice on this site for homework-y questions), but it's not actually graded homework. I'm just doing problems.
Mar
27
accepted In $PdV$, what is the value of $P$? $P_1$ or $P_2$?
Mar
27
comment In $PdV$, what is the value of $P$? $P_1$ or $P_2$?
I did figure it out. But it's still nice to have an answer to accept. I realized that $U_2 - U_1$ only depends on $T$ and not $P$ but only after I searched my formulas. I dont quite remember all of them yet. But still, thanks!
Mar
27
asked What is the meaning of $h_L - h_H$ for a heat engine?
Mar
27
comment In $PdV$, what is the value of $P$? $P_1$ or $P_2$?
Thanks. Okay, I think I have something. Is it $-W_{12} = U_2 - U_1$? My $U_2 - U_1$ can be taken from my values of pressure and temperature. And there is my specific work. Thanks for the hints (if this is right)!
Mar
27
comment In $PdV$, what is the value of $P$? $P_1$ or $P_2$?
Oh, wait, do you mean that the function of increase is linear?
Mar
27
comment In $PdV$, what is the value of $P$? $P_1$ or $P_2$?
I think you're implying the pressure is constant... which would make sense as the set up is a piston cylinder. But I've been given values for $P_1$ and $P_2$. I'm really sorry for not knowing, but I honestly don't know.
Mar
27
revised In $PdV$, what is the value of $P$? $P_1$ or $P_2$?
edited tags
Mar
27
comment In $PdV$, what is the value of $P$? $P_1$ or $P_2$?
Ah. Unfortunately I'm not given that function. Is there another way for me to get the specific work?
Mar
27
asked In $PdV$, what is the value of $P$? $P_1$ or $P_2$?
Mar
23
comment Future light cones inside black hole
Since the timelike and spacelike dimensions flip inside a black hole, can you avoid getting older when you cross the event horizon? Even more, can you reverse your aging (just as you can turn around in space)?
Mar
21
comment Where are we : On level ground or on a ramp - moving in a train?
Why would he mention the pendulum if he didn't want to know about it? Disregarding that is functionally the same as "can we comment where we are... if I'm eating lunch too?" The fact you eat lunch doesnt have to do with anything -- but a pendulum might. Wouldn't that be why it's mentioned in the question? I'm not disputing your answer. You're quite correct. But isn't it interesting to wonder if the pendulum would tilt to one side when the train gets on the ramp?
Mar
21
revised How to solve state parameters using these givens for an ideal gas?
added tags
Mar
21
comment Where are we : On level ground or on a ramp - moving in a train?
But the question was, can we do it by observing the pendulum? That is, will it "tilt" towards one side? I think it's the same thing as asking, if we have water in a glass and the train goes up the ramp, will the water level, from my perspective, tilt?
Mar
21
comment How to solve state parameters using these givens for an ideal gas?
But then I would need to know $E$, $v$ and/or $u$, since I don't know these values yet. Honestly, this is a basic thermo class, and I'm not sure if the inlet and exit velocities are useful or just a red herring, but my teachers feel like giving us a hard time.
Mar
20
comment How to solve state parameters using these givens for an ideal gas?
The only thing it says in there about turbine efficiency is already written above: $\eta = \frac{w_{actual}}{w_{isentropic}} = \frac{h_i - h_e}{h_i - h_{e)s}}$. That's my problem, because I only solved for the isentropic $T_e$ but I know that my process isn't really isentropic, and I'm having a hard time finding the real value. Isn't that metric $h+1/2V^2$ applicable only to a reversible, isentropic case? Or am I wrong?