The h Bar

Future Historian

3:00 PM

@Semiclassical? How much power do the various types of main sequence stars generate?

Semiclassical

how tf would I know?

Future Historian

G class stars generate 10^26 Watts for a K2.0 civilisation.

Just asking.

Yuzuriha Inori

@Semiclassical First, here there won't be a square on $w$

Future Historian

But the other stellar types elude me.

Semiclassical

@YuzurihaInori why? $d(1/w)/dt = -1/w^2 (dw/dt)$

Yuzuriha Inori

3:03 PM

$J_d=\rho\vec{v}=E\epsilon_0dw/dt=(V\epsilon_0/w) dw/dt$

Semiclassical

What?

Balarka Sen

You're computing the displacement current. There's going to be a time-derivative of $E$ in there.

Well, displacement current density, w/e

Semiclassical

yeah. $J_d = \epsilon_0 \partial_t E = \partial_t (\epsilon_0 V/w) = \epsilon_0 (V_0/w^2) (dw/dt)$

the basic issue, though, is that in the second case it's seemingly the case that $J_d=0$ within the capacitor; a use of the Maxwell form of Ampere's law is then enough to assert $B=0$ within the capacitor

Yuzuriha Inori

Okay yeah, I did a small algebra mistake

Semiclassical

Maybe it's just a consequence of ignoring the fringing fields. the electric field is not going to be constant in time out there

Yuzuriha Inori

3:10 PM

Take infinite plates. Still this occurs

Semiclassical

eh. with infinite plates you don't get a magnetic field at all in either case

Yuzuriha Inori

That's what I am saying. The second case is consistent with that.

Semiclassical

hmm

Yuzuriha Inori

I am checking the first case

Semiclassical

well, in the first case you definitely have a time-varying electric field and therefore a displacement current

and therefore a magnetic field

Yuzuriha Inori

3:12 PM

True

But why does it disappear? Maybe because the external source of energy disappears...

Hydrous Caperilla

1

Q: Atmospheric pressure And heat convection

If hot air rises due to convection, why does it get colder when we climb mountains? After some research, I found out that atmospheric pressure affects the temperature of the surroundings. Another question arises: How does atmospheric pressure affect the surrounding temperature?

Semiclassical

well, you still have to apply energy to put the plate in motion

Yuzuriha Inori

That's the same in both cases. If we shift our zero energy, it won't matter.

Semiclassical

my guess is that there's really two contributions to the displacement current, one arising from the fringing fields and the other from whether the charge on the plates is changing

in the second case, you only get the first contribution

in the first, you get both but one can claim that the first term is small compared to the first

that's not something I can see how to back up, though

i can't see a clever approach either

Yuzuriha Inori

Well I see something. In the second case, our volume is decreasing when we move the plate. The electric field has to increase and wouldn't that create a magnetic field?

Semiclassical

3:18 PM

why would changing the volume change the electric field? the electric field is dictated by the charge distribution, and in the second (isolated) case that never changes

more precisely, the electric field between two oppositely-charged parallel plates is dictated by the charge density $\sigma$ as $E=\sigma/\epsilon_0$

Yuzuriha Inori

Oops oops... I used a wrong density

Hmm

Semiclassical

np. my statement is only true between the plates, of course, and in particular it's not valid near the edges

hence why I think the issue has to be the fringing fields

Yuzuriha Inori

I also can't think of anything else now. Gimme some time to think.

Semiclassical

np

Yuzuriha Inori

Try to see how the total energy changes when there's no external source. Maybe that might help.

Semiclassical

3:22 PM

right

Anonymous

@BalarkaSen Thanks for writing it out. I'll read it properly during the weekend. (exams going on this week :P)

Balarka Sen

No problem! We could talk about it after both of our exams are done, perhaps

I wanted to learn persistent homology at one point but never got around to it

Anonymous

Sure. Your is getting over on 24th right? Both CMI and ISI ?

Balarka Sen

Oh no much earlier, 15th

Anonymous

Oh, nice! Our last test has been postponed to 26 th due to the elections, but we do have holidays in between. Let's see. :)

Balarka Sen

3:33 PM

mmkay

Anonymous

See you around, going off now :)

Balarka Sen

bye

Semiclassical

I think my conclusion right now is that, while there will be a displacement current due to the fringing fields in the second (isolated), said current is restricted to the edges and is an order of magnitude smaller

CooperCape

4:14 PM

boo

ACuriousMind

4:29 PM

@CooperCape ahhh

... ruined.

rueeened

...what?

I ruined you

cause you got scared

enumaris

rueened

ACuriousMind

4:34 PM

Right.

CooperCape

uh...huh.

Balarka Sen

ruined is the british way of saying "rekt"

you just got rekt my dude

CooperCape

pretty much yer

@BalarkaSen How's the organic chem going?

John Rennie

I'm British and have never said ruined to mean rekt

CooperCape

I just started properly revising it this week...

Balarka Sen

4:37 PM

@CooperCape me done doing high school

no chemistry anymore on my town

CooperCape

Oh shoot

nice oneeee

John Rennie

The word used to be used to describe a woman who had premarital sex, though I don't suppose anyone has used the word that way for fifty years, possibly longer.

Balarka Sen

:grimace:

CooperCape

I finish chem 20th June :/

Yeah perhaps not the politest use...

ACuriousMind

@BalarkaSen So whatcha doing now (except drugs)?

Balarka Sen

4:39 PM

well, nowadays, the husband is associated with an adjective than the woman

so i presume that's an improvement

Anonymous

Is it weird that I'm listening to Taylor Swift songs to keep myself awake before exams ?

CooperCape

Nah I love a bit of TayTay

John Rennie

Taylor Swift?

CooperCape

My favourite is "Look what you made me do" for the... incredible chorus.

John Rennie

Remember that credibility you used to have? :-)

Anonymous

4:40 PM

@JohnRennie Yeah, the new ones like Bad Blood

Balarka Sen

@Blue Plebian

Anonymous

:P

Anonymous

It's good drug

Balarka Sen

@ACuriousMind Going to take a few admission exams for the few universities I want to get admitted in

Not sure if I'll get in but I'll try

If I don't I'll probably abandon math

enumaris

a few?

Balarka Sen

4:41 PM

Be an electrician or something

enumaris

u gotta take diff exams for diff unis?

what

Balarka Sen

@enumaris By which I meant 2

Yes

Anonymous

@CooperCape Ya, I do like that one! Except that I'd like it even more if it repeated the same line a few less times

ACuriousMind

@enumaris Don't try to understand the Indian education system :P

Balarka Sen

We don't have SAT unlike US

enumaris

4:42 PM

seems inefficient...

Balarka Sen

Uh, kinda.

CooperCape

@Blue Ooh look what you made me do, look what you made me do. Look what you just made me do look what you just made me ooh!

enumaris

is this for undergrad or grad?

Balarka Sen

@CooperCape Lyrics brought to you by Lil Pump, Harvard Graduate

@enumaris Undergrad

Anonymous

@CooperCape Lol..yeah :D The ending is hilarious though. There's some amount of novelty in the videos

enumaris

4:44 PM

hmmm...

for undergrad I applied to 10 schools

that's 10 exams

seems like a nightmare

lol

Balarka Sen

tis hard

CooperCape

I had to do an entrance exam for one of my unis...

Pretty sure I failed it.

Chakrapani N Rao

4:56 PM

@CaptainBohemian "I read your question on Sat. but felt what you said is irrational based on my knowledge in a lot of places so didn't know how to reply you"

Thanks for taking time, I know that most probably I am wrong, But I just want to know how, if you could explain what are irrational parts, I will be more than helped, You can still find the question here physicsponder.quora.com

CooperCape

you crazy

Secret

Maybe not so fast, the Readings are still not fully determined yet

Chakrapani N Rao

Why would a question be removed?? how can a question be wrong?

enumaris

could be off topic

like if u ask a question about literature in the physics SE

Chakrapani N Rao

yes but if it regarding physics itself, then?

Atleast how is my question off topic??

enumaris

5:03 PM

no idea, I never saw your question

Chakrapani N Rao

qr.ae/TU1mXG

if you are interested

ACuriousMind

@ChakrapaniNRao Your question was closed for being unclear, not for being off-topic, and it was then deleted by an automatic routine that deletes negatively-scored closed questions without answers after a week. You had a week to address the issues raised in the comments and fix it to get it reopened, but you didn't.

Chakrapani N Rao

oh ok , I didn't know this, I am new here

enumaris

does anyone know which stack exchange site I should post questions about NLP to

is it the data science stack exchange...

ACuriousMind

@enumaris If you tell me what NLP stands for, maybe :P

enumaris

5:10 PM

natural language processing

Alex K Chen

Hello

enumaris

there doesn't appear to be a specific SE for it, and data science feels the closest...but natural language is like a bit different from the statistics related questions on there

Anonymous

@enumaris Data Science SE

enumaris

ok thanks

Chakrapani N Rao

oh I have a comment from @ACuriousMind

ACuriousMind

5:11 PM

@AlexKChen I have asked you multiple times now not to post your questions here directly after you ask them. Why do you continue to ignore that?

Alex K Chen

OK Sorry.

But do you know the answer to that question ? @ACuriousMind ?

ACuriousMind

@AlexKChen I did not read your question.

Chakrapani N Rao

"It is wholly unclear where you're pulling these values for the uncertainties from, or why you think uncertainties would change over time." Uncertainty of position will not change but Uncertainty in momentum does as time evolves, because if it had higher velocities the particle would have hit the wall

ACuriousMind

@ChakrapaniNRao We've already explained to you at length in this chat what's wrong with that line of thought. If you have nothing new to offer, this is not going to be a productive conversation.

Alex K Chen

Is it OK to bump old question to which I don't have any idea ?

Chakrapani N Rao

5:14 PM

"We've already explained to you at length in this chat what's wrong with that line of thought" this is completely wrong

no one has clearly said me why its wrong

ACuriousMind

@AlexKChen What do you mean by "bump"?

Alex K Chen

3

Q: Why, exactly, can't two field lines cross?

My physics textbook says two electric field lines never intersect. Their explanation runs somewhat like this: If two field lines crossed, there would be two different directions to the electric field at the intersection point, which is impossible by definition. A similar explanation is prov...

electrostatics electric-fields

I have the exact same confusion

Chakrapani N Rao

for once give me a proper answer and I will hold my peace

And I will be genuinely grateful for you

ACuriousMind

@AlexKChen And what is insufficient about the answers to the linked duplicate?

Alex K Chen

Well doesn't the answers in the linked question dupe says that it's not possible because you can have two different tangent directions ?

Chakrapani N Rao

5:19 PM

ok if anyone has an answer feel free to ping me

ACuriousMind

@AlexKChen Exactly - the tangent to an intersection would be undefined, i.e. the electric field at the intersection point would be undefined (which is exactly why the electric field at the location of an ideal point charge is undefined).

Chakrapani N Rao

and please.., no my question is not properly refuted, it was just simply called out as outlandish, never was a proper explanation given, you can examine the older chats

bye physics community, see ya, gn

enumaris

5:42 PM

data science SE is so small..-.-

not even 10k questions

gonna take forever to wait for someone to even see my question :(

Anonymous

@enumaris Well, it is a beta site. Area 51 says that the answered questions percentage is 75.

enumaris

hopefully what I'm asking actually has an answer lol

Anonymous

SO has a NLP tag

Anonymous

stackoverflow.com/questions/tagged/nlp

enumaris

yeah but my question isn't really coding related

I've been told to take non-coding related questions elsewhere

Anonymous

5:47 PM

cs.stackexchange.com/questions/tagged/…

Anonymous

stats.stackexchange.com/questions/tagged/natural-language

enumaris

oh...there's actually a related question in SO lol

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