The h Bar

vzn

04:36

BEAT SABER ON DEDICATED VR ARCADE CABINET

►

dm__

05:05

where is everyone?

user8718165

05:23

hello sir@JohnRennie

John Rennie

@user8718165 morning :-)

user8718165

I have some doubts. are you free now sir? @JohnRennie

John Rennie

@user8718165 yes, I'm around for a few hours

user8718165

Ok sir asking...

How can the ammeter show no deflection in this image?I think the current should always be flowing through the ammeter imgur.com/a/teadlly

Is this image correct @JohnRennie

John Rennie

05:38

@user8718165 The I = 0 label applies to the salt bridge between the two beakers, not to the meter. The meter is a voltmeter not an ammeter.

It means the current is zero where I've indicated with the red arrow.

The current is zero because the circuit is applying an external EMF to the cell and stopping the reaction in it.

user8718165

Why is that thing not an ammeter?

John Rennie

It's a voltmeter measuring the voltage across the cell.

user8718165

so it should show 1.1V and deflect sir...I think...but it is not deflecting

I've got two more images which I've included. What voltages will the voltmeter show in each case?

John Rennie

@user8718165 I'm not sure I would take the diagram too literally. I suspect the vertical arrow in the circle is just the symbol for a meter, not that it's showing zero deflection. As you say, the voltmeter would read 1.1V.

user8718165

Ok thank you very much sir. Last thing, could you please tell me why would the voltmeter deflect left or right in the following two images? imgur.com/a/teadlly

John Rennie

05:54

Ah wait. I think there's an error in one of the diagrams. The battery has been drawn the wrong way round ...

user8718165

Ok sir no problem @JohnRennie

John Rennie

Those diagrams don't make sense to me. I don't understand what that meter is supposed to be showing. In the second two diagrams it does look like an ammeter, but that doesn't make sense..

user8718165

These are the diagrams from my ncert book. I tried hard the last day to get these but couldn't. These images don't make sense to me either.

@JohnRennie

John Rennie

@user8718165 I think they are just saying that if you apply an external EMF to the cell you can stop the reaction or even drive it backwards. But that meter is in the wrong place on the diagram.

I think it should be like this:

user8718165

@JohnRennie was thinking the same way since yesterday because I learn't about potentiometers a few days ago but I thought I was wrong...thank you very much sir😊😊

John Rennie

06:10

@user8718165 that's why at first I thought it must be a voltmeter not an ammeter because it's in the position where you'd put a voltmeter.

user8718165

@JohnRennie Ok sir also it makes sense that ammeter shouldn't be where it was because that would short out the electrolytic cell right?

in the original diagram

John Rennie

@user8718165 yes, exactly.

user8718165

@JohnRennie Thank you sir for assistance..😊

John Rennie

You're welcome :-)

dm__

07:54

anyone ever tried to plot TM or TE modes in mathematica for a coax cable?

user351417

08:08

0

Q: How to determine donor or acceptor impurity

I am working on a practice exam for semiconductor physics. Can anyone help me figure out how to determine whether we have donor or acceptor impurity in Gallium Arsenide? Gallium is column 3 and (I think) it has a valence of 3. Arsenide is column 5 and (I think) it has a valence of 5. But it has ...

user351417

I'm out of close votes, but I think that one's off-topic. I found it while running data.stackexchange.com/physics/query/edit/991380

user351417

Could someone send it to the queue?

dm__

woah, I think it worked. TE11 mode for coax cable:

those are the E field lines

John Rennie

09:10

@Chair wow, it's 9 a.m. and I have only three close votes left

user351417

09:22

@JohnRennie I've been spending less time on reviews lately, so this is the first time this year (if I recall correctly) that I did 20 close reviews and/or used up those VtCs.

dm__

better depiction:

but I feel something may be off on the outer perimeter, as those field lines clearly appear to have a non-zero tangential component. hm.

guessing it's a resolution issue with the StreamPlot function

user351417

10:37

Many thanks.IMpact force = mv^2/s = mx30^2/0.8 — Beccy 11 mins ago

user351417

lol that's weird context for "Many thanks."

PM 2Ring

11:18

There's an interesting puzzle in a current xkcd science forum thread: Extracting energy from a black hole via gravitational blueshift. I think I've solved it, but I'm not 100% certain. ;)

Rudi_Birnbaum

12:30

@EmilioPisanty: Am still chewing on the units of the delta function. I would be inclined now to use $\delta(\alpha x)$ instead of $\delta(x)$ where $\alpha$ is the unit lengths.

reciprocal unit length i mean

Emilio Pisanty

13:02

@Rudi_Birnbaum well, there's nothing stopping you

It's not a common choice, but it's a valid way to go about it

if there is a natural length scale you can use

Which there often isn't

So you might as well learn to handle it in full

user351417

13:29

2

Q: Usage of “eigen” to mean “to belong”

I recently came across this sentence with the following translation: Sämtlich waren sie dem Staat eigen. – They all belonged to the State. So far, I have not seen such a construction with eigen and guess that the general construction is etwas jdm/etw(dativ) eigen sein. Is this correct? Source...

word-usage

user351417

I didn't know that one.

user351417

HNQs are fun!

GodotMisogi

13:45

"I f*** with quantum physics" is going to be my new pick-up line

Yellow

14:18

I want to puke after reading that

Is there a list of particles and atoms with mass, magnetic moment and spin1?

ACuriousMind

@user212860 Almost all the particle info you'd ever want is at pdg.lbl.gov/2018/tables/contents_tables.html

user212860

thank you

Anonymous

14:35

@user212860 QMechanic's gravatar? :P

ZeroTheHero

15:15

@EmilioPisanty I'm trying to download the Mma field line code you linked me to the other day but no joy.

"page not found"... :(

Emilio Pisanty

16:36

@ZeroTheHero what did you run within what application?

The message starts with Import and then has two URLs as consecutive arguments

You need to run the whole thing in mma

  Import["http://halirutan.github.io/Mathematica-SE-Tools/decode.m"]["https://i.sstatic.net/oiLr8.png"]

Copy and paste into a mma cell, then run

The first argument is a decoder script

The second is the mma code, encoded as an image

Avnish Kabaj

what is this witchcraft

i remember one of my friends in eight grade who used to hide homework folders in images

John Rennie

@EmilioPisanty this is what it did here:

Is that the expected behaviour?

And it drew this:

ZeroTheHero

17:04

@EmilioPisanty ok I wasn't doing this right... I was just trying to download a code from github.

The version I produced is

It's unexpected that Mma can't do this "built in".

(with correct axes now... :))

anyways thanks for being on my toes.

Emilio Pisanty

17:24

@JohnRennie yes

@ZeroTheHero indeed

See my question on mma.se

But it's a hard problem to do this properly

Particularly if you don't have a stream function

7

Q: How can one produce a proper streamline plot?

I recently had trouble producing a proper streamline plot in Mathematica, and apparently the problem is a good bit harder than I appreciated. I would like to know if there exist general algorithms to produce streamline plots which deal appropriately with line spacings and terminations. Let me ma...

visualization plotting vector

48

Q: New SE-Tools - formerly known as SE-Uploader

I have completely revised our old SE-Uploader and finally finished putting all together in a package called the SE Tools. Therefore, we can now provide additional features because the SETools` can be loaded. Currently, the uploader palette is still the largest part of the software. I have put muc...

discussion

ZeroTheHero

wow this is quite useful.

Emilio Pisanty

Yes

It is

Install it

And watch your life get easier

ZeroTheHero

well to tell you the truth right now I have too many balls in the air but it's on the todo list.

Emilio Pisanty

It's super easy

ZeroTheHero

I love the way your generation is so comfortable with this kind of stuff.

Emilio Pisanty

17:32

I mean

It's literally just running one mma cell

(if you trust the mma.se mods with installing software in your machine, of course. But if you don't, and you have good reasons not to, then the Internet is a pretty hostile place for you.)

pZombie

17:50

I don't get it. I am being told that pilot wave theory is equivalent to quantum mechanics as far as predictive power goes but then i come across articles like this sciencealert.com/… ... which suggest otherwise

Emilio Pisanty

@pZombie the fact that an analogous theory (allegedly) works, in a separate domain, is in no way evidence that the original theory works, or is a correct description of nature, in its original domain

Enthusiasts of pilot-wave theory tend to make substantial amounts of noise any time an analogous theory comes around, despite the fact that such a theory has nothing at all to say about the original context

This is clearly exhibited in the handling of the bouncing-liquid-droplets analogy, which is similarly mum in its implications to QM and its interpretations

A cynic might say that this extreme emphasis on useless analogies is an indication that the original theory doesn't work

2

As for this newest "pilot-wave gravity"... if it's still alive in three years' time and it's been used to solve more than a single problem, then it starts paying off to look more closely into it.

vzn

18:05

@pZombie lol nothing to see here move along folks™ ... there is a lot of new/ bubbling developments in PWH theory but so far it hasnt much scratched establishment theory. so here you see a glimpse of the red vs blue pill™... :o o_O

Anonymous

How can I search for images I've uploaded in chat?

Anonymous

Whew, finally! I was under the impression that it's simply not possible to search for images in chat.

PM 2Ring

@Blue Interesting! I usually just do a search for the file extension: png, gif, or jpg. I wish we could use SVG...

Anonymous

@PM2Ring Oh, that's a good idea too. I sometimes use "i.stack.imgur.com", but that only works for images which were uploaded to Imgur. :)

Anonymous

Yeah, SVG would be nice. I'd also like PDF uploads in chat. But that might be a bit heavy. :P

Anonymous

18:18

Might work fine with some size restrictions.

PM 2Ring

18:38

@Blue :) I guess single page PDFs could be ok, but otherwise it'd be a nightmare. And we couldn't expect the SE devs to incorporate a full PDF viewer into Chat.

Allegedly, ghostscript can render to SVG, but I don't think I've ever tested it. But I've often used it to convert hand-written PostScript to PDF.

dm__

21:03

fixed it. TE11 mode for coax cable:

dmckee

23:19

Comparison of classical and quantum position probability distribtutions for the HO:

The solid blue lines represent the classical result, the dotted red line the quantum result.

Note that the quantum result leaks into the classically forbidden zone and that the correspondence gets better for higher energy.

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