STUPID QUESTION THREAD

[STUPID QUESTION THREAD No.7284872]

Other one is at bump limit.

Can someone explain how to draw vectors out of a compound(?) vector??
Not english but you get the point.

[Anonymous No.7284979]

>>7284872
Bump

[Anonymous No.7284984]

Can you prove that a relation is not able to be injective by showing the cardinality of the domain set is less than the cardinality of the codomain?

Like would that make sense as a proof? Because from what I understand a relation cannot be injective if there are more 'a' than 'b' because then each input cannot get its own unique output.

[Anonymous No.7284992]

What are the BEST Precalculus and Calculus books to really understand the concepts?

[Anonymous No.7285053]

bumpin

[Anonymous No.7285056]

>>7284872
What are some cool experiments to do at home?

[Anonymous No.7285074]

http://nrich.maths.org/2200

Public key cryptography. I understand how to do it, but what I don't understand under what concept Bob decrypts the message. Like, what principles are at work? How does it go backwards?

[Anonymous No.7285076]

>>7285061
Con't from previous thread, yes it can. How stable it is will depend on what is the exact ion, but something like a fluoride ion will be more than happy in a vacuum.

[Anonymous No.7285084]

>>7285074
the entire encrypted messaging process is like sending someone a letter inside a safe. Public keys are the safes and private keys are the secret combinations that open the lock.

Message is written and placed inside the safe then you spin the dial (public key), encrypting it. The person receiving it has a special combination (private key) that opens the random encrypted message.

In actual computing the public key just performs a mathematical operation on the binary of the file you encrypt and the private key is the only key that is able to reverse that operation. The actual math is super complex and has something to do with entropy.

[Anonymous No.7285092]

>>7285084
I understand the jist of it, and I did it multiple times on paper with small numbers.

The problem I'm having is what the fuck is happening with the math that makes this possible.

[Anonymous No.7285110]

>>7285092
entropy. Your computer collects a lot of data from random sources like mouse movement, key presses, processes and it uses that data in the encryption formula. Thats how it guarantees an almost random result everytime. Private key just reverses the original formula.

[Anonymous No.7285115]

>>7284992
Go to /sci/ wiki see textbook reccomendations

[Anonymous No.7285132]

Is there anything besides chance to Roulette at a casino?

[Anonymous No.7285150]

>>7284992
yeah unfortunately this kind of question does deserve its own thread seeing as it's stickied

[Anonymous No.7285158]

>>7284872
The more I think about this, the more it annoys me.

Let's take the binomial distribution.
1) There are only two possible outcomes, success or failure.
2) The probability of success, p is constant.
3) The number of trials, n is constant.
4) Trials are independent.
How can #4 ever be necessary? Surely if the probability of success is constant, then no one trail has had any effect on the others, so it follows that trials are independent.

Am I brain-dead?

[Anonymous No.7285164]

>>7285158
I feel like you just explained why its there

also bump >>7284984 for my discrete math people here

[Anonymous No.7285165]

>>7285158
Let's say that there is a system and you're trying to measure the results if or when event A happens, and event B is a failure. If the trials are not independent and B can affect the chance of A happening it totally changes the problem, thus they need to be independent.

[Anonymous No.7285174]

>>7285056
the EM drive

[Anonymous No.7285179]

>>7285165
>B can affect the chance of A happening
If that is true, then "2) The probability of success, p is constant" is not true, hence my problem of not being able to see how #4 can be false when #2 is true.

[Anonymous No.7285189]

>>7285179
2 is only false when 4 is also false in that situation.

[Anonymous No.7285191]

>>7284984
what do you mean by relation?

A function cannot be injective if the domain has larger cardinality than the codomain. This is obvious for finite sets and somewhat less obvious but nevertheless true for infinite sets

[Anonymous No.7285203]

>>7285189
That's my point, when can 2 be true if 4 is false?

[Anonymous No.7285207]

>>7285191
I was looking at this wrong, its a function of a relation of two sets. Yea I see how it is obvious, I'm just not confident writing it as a proof.

I imagine something like: Card(A) > Card(B), not Inj(α).

Thanks for letting me know I wasn't retarded about the first part.

[Anonymous No.7285212]

>>7285203
Your question was "when can 4 be necessary?"
So that's what I was answering. The outcomes have to be independent to keep P constant, or else they're dependent and P isn't constant.

[Anonymous No.7285229]

>>7285212
But if P is constant, how can the outcomes not be independent?

[Anonymous No.7285246]

>>7285115
>>7285150
The wiki says stewarts for precalculus and Spivaks for calculus but when I ask in other threads Some people says they are shit and some other people said they are great books, who do I trust?

[Anonymous No.7285268]

>>7285246
Spivak and Stewart are great books, people just try and troll or complain because they aren't for the autistic

[Anonymous No.7285274]

If c is the speed of light which is a constant
then why can't we just say E = m^2?
What is the unit of engergy?

[Anonymous No.7285284]

>>7285229
Not that guy, but specifying the marginal distribution for each trial doesn't say anything about the joint distribution. For example, if X~Binom(1, p) and Y~Binom(1,p), then we have p(x) = p(y) = p(1-p). However, it is possible that p(x, y) ~= p^2*(1-p)^2 in which case X+Y need not be binomial distributed.

For a simple but somewhat contrived example, imagine I have a math test consisting of 10 quadratic equations, which I give to a randomly chosen person off the street. For each question, let Xi be the random variable that = 1 if he knows how to solve question i, and 0 otherwise. We may consdier Xi~Binom(1,p).

However, if you know how to solve one equation, you can solve them all (at least, let's assume that for the sake of the example), so the statement "P(Xi = 1) = p" really boils down to saying "the probability that a randomly chosen person knows the quadratic formula is p".
In this case, the total score (sum i=1 to 10)Xi will equal 10 with probability p, and 0 with probability 1-p, which is not binomial. This fails precisely because the 10 trials are not mutually independent.

[Anonymous No.7285295]

>>7285284
Correction:
>we have p(x) = p(y) = p(1-p). However, it is possible that p(x, y) ~= p^2*(1-p)^2
Specified the binomial formulas wrong; that should be:
"p(x) = p^x * (1-p)^(1-x), p(y) = p^y * (1-p)^(1-y); however it is possible that p(x,y) is not equal to p^(x+y) * (1-p)^(2-x-y)".
In other words, X+Y is not Binom(2,p) distributed.

[Anonymous No.7285310]

>take adderall

>do everything but study

hm?

[Anonymous No.7285314]

anyone have any experience or knowledge of doing an engineering phd in the uk? Love academics and research and not motivated by money. Have a 1st class masters from a Russel Group uni. Will it be difficult to get a position?

cheers

[Anonymous No.7285315]

>>7285274
Because m^2 is parabolic and totally different than m(c)^2 which is linear.

[Anonymous No.7285329]

>>7285284
Hmm, let me make sure I've got my head around this.
p is the probability that ONE SINGLE PERSON successfully solves a quadratic.
Give said person 10 quadratics, so X~B(10,p).
Then, despite the fact that:
1) There are only two outcomes.
2) The probability that A GIVEN PERSON knows how to solve a quadratic is assumed to be constant.
3) Our number of trials is constant.

This situation will not be well modelled by a binomial distribution, because the outcome of one trial is dependant on another - if you can solve one quadratic, you can probably solve, most, if not all of them.


That seems to work perfectly, but bloody hell that's hard to spot, I can't even get the wording in a way I'm happy with, any tips? It seems that it all comes down to how you define p.

[Anonymous No.7285402]

>>7285314
Would like to know this as well. I'm an international student meeting the "requirements" I need in terms of grades to get into any UK uni PhD programme, my question is how competitive is the engineering school selection at the top schools and is it mostly based on research or grades past the minimum entry requirements? Or does everyone just get in and then compete for grant money like in my country?

[Anonymous No.7285409]

Who are the best scientists?

And why are they all Russian?

[Anonymous No.7285425]

>>7285268
Thanks

[Anonymous No.7285464]

>>7285314
>>7285402
Heck, if either of you know. I'm interested in how UK Professorships work.

[Anonymous No.7285709]

Great intro to proof book?

[Anonymous No.7285856]

>>7285076
Interesting.

How would you go about proving that a certain atomic combination of (e's, n's and p's) is stable in vacuum?

What about guessing whether an ion is stable vacuum?

[Anonymous No.7285861]

>>7285409
Stop your shitposting, the filename gives you away every time.

[Anonymous No.7285941]

>>7285132
>>7285132
anyone?

[Anonymous No.7286028]

why do I feel stupid. I read posts here, on /int/ and on /g/ and I feel stupid and like an imposter if I try to join even if I have some idea of whats being talked about.

[Anonymous No.7286032]

If i get a chemistry undergraduate degree, is it possible to go to a molecular biology graduate program? I'm much better at biology, but I'm not interested in zoology or evolutionary or ecology or any of that soft science shit, and a university offered me alternate-acceptance for chemistry with a $1000 scholarship. is it worth the risk of being stuck in the wrong program until i can switch? how hard is it to switch majors? how hard is it to double major? should i just stick in a chemistry program and take bio electives / self-study, what do i do I'm a molecular biologist at heart but it's a really good school and they offered me MONEY for chemistry undergrad.

[Anonymous No.7286042]

>>7286032
Yes, but man a 1k scholarship is nothing and definitely not worth it if you'd rather want to do a bio undergrad. A Chemistry undergrad will be better if you want to do molecular bio in grad-school.

[Anonymous No.7286067]

>>7285274
There is a unit system based on the speed of light set at 1

[Anonymous No.7286251]

How did the engineers are gay meme come about?

[Anonymous No.7286308]

>>7286251
While I am interested, I was under the impression that it's true, in America at least.

[Anonymous No.7286315]

Will we ever terraform and colonize our solar system and beyond?

[Anonymous No.7286323]

>>7286315
Probably not Mercury or Venus, they're too hot.

[Anonymous No.7286334]

>>7286323
What about Luna, Mars or the Jovian moons?

[Anonymous No.7286409]

why does my throat itch when i clean my ears with a q tip

[Anonymous No.7286935]

I know perpetual motion does not exist, but some devices using magnets are giving me a hard time seeing why it does not work.

Why do magnets not work for perpetual motion?

[Anonymous No.7286959]

>>7286315

That would probably take more energy than just living in metal bubbles on Mars.

[Anonymous No.7286963]

>>7284872
compound as in containing imaginary components? you cant draw them unless you use a circle to represent the irrational component, even then they wont make any physical sense so drawing them is pretty much pointless.

[Anonymous No.7286965]

>>7286935

Friction.

>>7286409

Dunno, image might have something to do with it. Maybe your brain just thinks that part of your throat is about to be touched.

[Anonymous No.7286999]

>>7286409
Some nerves dedicated to completely different things come close to each-other, and sometimes some electric signal just jumps from one to the other. e.g., sneezing when you see excessive sunlight, throat itch or watery eyes when you put something in your ears.
Also q-tips are bad for your ears and shouldn't go in there

[Anonymous No.7287046]

looking for an organic chemsitry I book, that teaches me everything I need with exercises and solutions for fast understanding?
I am already working on david r. klein's organic chemistry as a second language and should be through it in three weeks and another week for review.

[Anonymous No.7287051]

Are there any eukaryotic, single-cell, organisms we know of?

[Anonymous No.7287056]

How can a ship continue to accelerate when under the effect of relativistic time dilation? Won't the system's propulsion slow down in relation to it's surrounding space, thereby providing less actual thrust?

[Anonymous No.7287092]

Ok I have been thinking about this stupid problem for like half an hour and I came to the conclusion that there is no sufficient data:

"A gamma ray with a wavelenght l = 0.0062 nm hits an electron which is at rest. Calculate the wavelenght of the scattered gamma ray and the kinetic energy acquired by the electron."

This shit is about the Compton effect. Don't I need the angle between the original direction of the gamma ray and the direction of the scattered ray to solve it???

Pic fucking related

[Moose No.7287102]

>>7287051
http://en.wikipedia.org/wiki/Amoebozoa
?

[Anonymous No.7287133]

>>7287051
paramecium, vorticella, amoeba, etc, etc...

you never looked at a drop of pond water in a microscope???

[Anonymous No.7287243]

>>7287092
Yeah you do, or failing that, some info about the gamma ray's new energy, the electrons energy, or the new wavelength

[Anonymous No.7287250]

Should I study real analysis before calculus? are there any prerequisites to real analysis?

[Anonymous No.7287372]

Why cant there be a set of all sets?

Why do things emit infrared radiation if almost everything is made of neutrally charged atoms?

[Anonymous No.7287374]

Guys i need

[Anonymous No.7287384]

>>7287372
Suppose the set of all sets existed.
Then, that set contains the set that contains all sets that don't contain themselves.
Does that set contain itself? If so, then it can't contain itself by construction.
If it doesn't contain itself, then it would contain itself by construction.
A glaring contradiction.
So you can't have a set that contains all sets.

What do neutrally charged atoms and radiation have to do either each other? Electrons absorb and emit light, which is a form of radiation.

[Anonymous No.7287392]

Can someone please explain the difference between log and ln?

ln1 = 0, how?

log of natural number (e) 1 = 0, how?

Just use a calculator or is there an intuition behind this model?

[Anonymous No.7287400]

>>7287384
>What do neutrally charged atoms and radiation have to do either each other?
Heat? The kinetic energy of atoms in an object?
When they move, it's not only the electrons tat move, it's the whole atom

[Anonymous No.7287402]

>>7287392
ln x = log10 x

[Anonymous No.7287407]

>>7287402
So since log normally implies log10, lnx is the same as logx?

[Anonymous No.7287415]

>>7287407
yes

[Anonymous No.7287422]

Is heat transfer faster when the difference in temperature is higher?

[Anonymous No.7287426]

>>7287392
When you're a math baby, ln = base e, logx = base 10.
After first year math, logx = base e, and then you specify other bases. Ln notation is just for math kids.

[Anonymous No.7287526]

>>7285709
Book of Proof. I forget who write it,but I think it was some guy at VCU. It's on his webpage as a PDF.

[Anonymous No.7287530]

Why is linear algebra so useful yet so fucking boring in a linear algebra class?

[Anonymous No.7287557]

>>7284872
I know nothing about nerves and muscle control etc, but i was wondering.
With practice, would it be possible to control your heart muscle and induce death this way?
Like, focus really hard or something and stop your heart from doing anything.


Like people who never tried, cant muscle their breastmuscle(?) separately , but with enough practice you can.

[Anonymous No.7287559]

>>7287422

Yes. It's directly proportional.

[Anonymous No.7287562]

>>7287559
why? what happens at the atomic level?

[Anonymous No.7287578]

>>7287562

More average energy transfer per collision.

[Anonymous No.7287580]

>>7287578
are tere any programs that simulate this?

[Anonymous No.7287623]

How much faster than a regular base 2 computer would a base 16 computer be

[Anonymous No.7287626]

>>7287580

Simulate what? Collisions? Yes.

[Anonymous No.7287628]

>>7287623

Not faster at all.

[Anonymous No.7287635]

>>7287628
why not

[Anonymous No.7287663]

>>7287635

First, why do you think it WOULD be faster?

>inb4 "because 16 is bigger than 2"

[Anonymous No.7287670]

>>7287663
Because base 16 takes up much less space than binary.

[Anonymous No.7287672]

>>7287663
I don't know, perhaps it would save more space on memory? not sure if/how that would make it faster(Im no expert)

What about unary, is it not slower than binary?

[Anonymous No.7287687]

>>7287670
>>7287672

How would it physically take up less space? Something that had 16 different possible states sounds pretty complicated. In fact the simplest way to do it is probably just with four binary bits.

[Anonymous No.7287698]

>>7287687
>How would it physically take up less space?
not important, it's only hypothetical

[Anonymous No.7287713]

>>7287698

Well, it is important, since that's how you would answer the question.

[Anonymous No.7287720]

>>7287713
okay, let's say they are 16 different voltages(I know there are problems with that but pretend those problems dont exist)

[Anonymous No.7287732]

>>7287720

And how are they discriminated? Some kind of "switch" with 16 "positions?" But wait! You could do the same thing with 4 switches with 2 positions each. That's 8 positions vs 16. Sounds like binary wins.

[Anonymous No.7287751]

>>7287732
memeristors

[Anonymous No.7287853]

how to prove that
<span class="math">\frac{n^n}{3^n} \leq n![/spoiler]
by induction?

[Anonymous No.7287865]

>>7287853
Start with
<span class="math"> \frac{(n-1)^{n-1}}{3^{n-1}} \le (n-1)! [/spoiler]

Observe that <span class="math"> n - 1 < n [/spoiler] and then multiply by n.

[Anonymous No.7288377]

Can someone explain how i do this shit:


A company has fans blowing,(2,4MW), they blow for 5 hours straight.
The price of 1 kWH is 0.09$
How do i go from watt to watthour

[Anonymous No.7288383]

>>7288377
OH GOD I FEEL RETARDED,
I figured it out, dont mind this post.

[Anonymous No.7288412]

>>7284872
To those who have educated themselves through sticky, how much have you covered? How many years have you spent and approximately how many hours did you dedicate? Just curious, because the daunting amount of material overwhelms my pleb mind.

[Anonymous No.7288414]

>>7288383
watthour = watt * hour

[Moose No.7288416]

>>7288383
dont forget to convert MW to kW <3

[Anonymous No.7288965]

Guys, every time I go see my math teachers at this community college, I feel like I want to beat them up. However, they both seem like cool teachers, yet I have this feeling that I want to beat them up. Why is that?

[Anonymous No.7289212]

Does the increased mass of matter at relatavistic speeds increase its gravitic influence? I've read around on this and it seems to be a bit handwavy.

[Anonymous No.7289473]

I'm struggling a bit with analytical chemistry, mass spettrometry vs mass chromatography. Like, for example with proteins, when should I use Maldi-TOF instead of Capillary electrophoresis–mass spectrometry? I know the TOF is good for qualitative analysis so I should use Maldi-TOF for quali and CEMS for quantitative, but what's stopping me from using CEMS with a TOF?

[Anonymous No.7289480]

>>7288412
>To those who have educated themselves through sticky

lol, I don't think there are such people

[Anonymous No.7289481]

>>7285084
>something to do with entropy

[Anonymous No.7289483]

>>7288412
sticky sucks. wiki is better.

I've spent the last year or so working on real analysis.
I learned a lot, but haven't made it very far into any of my books.
I get really obsessive and have to prove everything to myself, even though most books skip certain steps

> how many hours?
maybe 5 hours a week?
not good at staying focused

> Just curious, because the daunting amount of material overwhelms my pleb mind.
just study what you're interested in.
I'm studying analysis to get a more formal introduction to calculus because variational calculus was too hand wavey for me.

[Anonymous No.7289487]

>>7285110
But your message isn't about entropy. I mean, that's a completely different thing.
/sci/ is supposed to be a science board. Don't say the word 'entropy' everywhere just because it's cool and HURRchaosDURR.
In both physics and CS entropy is a precise concept. And, I mean, that's not an esoteric mystery, you can google it in a sec.

[Anonymous No.7289489]

>>7285310
Assuming that 'hm' means 'Am I a useless faggot', then yes.

[Anonymous No.7289494]

>>7287557
http://en.wikipedia.org/wiki/Autonomic_nervous_system
you can't control your heart muscle any more than you can choose to secrete insulin

[Anonymous No.7289521]

>>7289480
I didn't mean "educated themselves through the sticky" as in a replacement for university tier education and instruction/training, but as a way to learn higher level material and broaden my mind. I just want to know how far one could go as an autodidact. I don't expect to become wizard scientist or whatever from this.

>>7289483
Thanks for the heads up. Rather strange that they don't just change the link in sticky to the wikia one if itsvbetter. Is there anything salvageable from the sticky's link though?

And it's cool to see someone make progress. Gives me hope that I can stop being so pleb haha

[Anonymous No.7290508]

Serious question /sci/
How come you people know so much?
I mean, i just started browsing /sci/, but i cant seem to understand how everyone on here has so much knowledge.

Where do you read all that stuff or is sci full of master degrees in math chemistry and physics?

[Anonymous No.7290515]

>>7290508
I think most of us here are Bachelor's students. If you study, it's actually not hard to learn a lot over a couple of years. I've only been in college two years yet I'd say I've amassed a sizeable knowledge of physics and mathematics.

[Anonymous No.7290544]

>>7290515
Alright, i thought so..
feel like im missing out because of not knowing that much.
I have no problem with learning or remembering stuff, its that i lack motivation to the point that i spend a full school year playing poker on my phone.

I have a half diagnosed ADD, but im still waiting on the actual results.
Could add be the problem here? i cant even read a text book because my eyes just do the movement and i zone out

[Anonymous No.7290558]

>>7290508
>How come you people know so much?

Most of the people who post here don't know much at all, they just give wrong answers that sound right to someone who knows even less than they do.

Also, obviously, it's different people answering different questions.

[Anonymous No.7290566]

>>7290544
It may be some of the problem, but I don't think it's all of the problem. Discipline is a skill you can train, and for most of us it's left completely untrained until college, because it's easy to breeze through high school without having to commit to studying for any length of time. So you have to put some time into 'training' it, by isolating yourself with your textbook for a while a couple of times a week, and over time you'll get better at being able to commit to studying.

[Anonymous No.7290616]

>>7290515
>I think most of us here are Bachelor's students
Or underage b&, but that being said, a lot of college students know a lot, particularly given how brutal age 16-18 education is in my country.

[Anonymous No.7290664]

>>7284872
How do you know if you're cut out for a career in the sciences?

I'm halfway through my physics undergraduate degree, but I'm questioning myself more and more everyday if this is really the path I want to pursue. I originally wanted to go as far as pursuing a phd and doing research, but now I'm not so sure anymore.

I love physics and science, but I don't know if I'd be any actual good in it in the real world. My motivation, my grades, and my effort have started dwindling because of these doubts.

I know that deep down inside I have somewhat childish dreams that are not very related to science at all - like programming video games for a living, for instance. But they're still aspirations even if they're less grand than aspiring to work at CERN or something. I've tried to do mental gymnastics as to how I could get there with a physics degree, like maybe programming physics in simulations and videogames. Maybe computational physics. I don't know.

I just know that I'm scared of dropping out and realizing I've made a terrible mistake, specially after already getting halfway there. But I'm also afraid that if I convince myself to push through it and I don't regain my love for the pure subject, and/or find ways to segway it into my aspirations, I'm going to become a bitter 20 something with no idea where to go.

[Anonymous No.7290673]

do you burn calories with your brain thinking really hard

[Anonymous No.7290956]

>>7287426
I still don't get it

[Anonymous No.7290969]

>>7290664

Computational physics is fucking awesome. Have you considered volunteering in a comp. phys lab?

[Anonymous No.7291280]

Someone remind me about conics and how a^2=b^2 + c^2 fits in?

If instead of 4^2 on the right it was 6^2, would that be the new a?

[Anonymous No.7291302]

>>7290673
www.youtube.com/watch?v=dHh5VCx3m-Y

Yes, but not much.

[Anonymous No.7291356]

>>7291280
It's to determine the foci.

Since it is a horizontal ellipse...

5^2 - 4^2 = 3^2
Foci are at (3, 0) (-3, 0)

[Anonymous No.7291367]

>>7285092
A very simple cipher to encrypt a message (basically the go to one for all textbooks to introduce the concept) is the Vernam cipher.

It is quite simple if you understand modulo 2 addition (think of an XOR gate). You have a bitstring which is your plaintext, i.e. the message you want encrypted. This is added to the key modulo 2 in order to obtain your ciphertext, i.e. the encrypted message which you send.

Example: I want to send the following bitstring
01100101
My key is:
10010110
Therefore the ciphertext becomes:
11110011

(Modulo 2 addition: 0 + 0 = 0. 0+1=1. 1+0=1. 1+1=0.)

The thing about this is that to decrypt the message you simply do modulo 2 addition with the key again:

ciphertext:
11110011
key:
10010110
plaintext:
01100101

Easy shit br000. The only problem is then for alice and bob to agree on a key without eve knowing about it.
The good thing about this cipher is that it holds Shannons something requirement(google it I can't know everything). Which means the ciphertext does not contain any information about the plaintext and thus cannot with any smart schemes be recreated, given that your key is completely random and will be changed for each new message sent.

[Anonymous No.7291544]

This is a really stupid question, but how do you store your experiment results file (assuming that we are using matlab and saving the results into .mat files).
My experiments depend on a lot of parameters so I named my files accordingly to the param and now it's a fucking mess:
result_lambda=001_leaves=4_ntree=5 [insert more params here].mat
What should I do?

[Anonymous No.7291563]

>>7291367
i literally just finished writing an encryption program like this in assembly for a class, but we were decrypting and encrypting strings.

[Anonymous No.7291565]

>>7284872
how would you use SPS to design a protein library with random sequences?

[Anonymous No.7291574]

What is the physical meaning of the electric displacement vector D?

[Anonymous No.7291607]

I frankly dont fully understand why batteries need a seperator.
Is there only purpose in preventing the electrodes form directly touching each other since modern batteries are so small?

[Anonymous No.7291627]

Is the minimal boolean expression F=B+C

[Anonymous No.7291643]

>>7291627
A'B'C'+AB'C'+AB'C+ABC'

AB'(C+C') + C'(A'B'+AB)

AB'+C'

[Anonymous No.7291653]

>>7291643
Btw you should understand why C+C' and A'B'+AB = 1 (see OR gates), and generally understand how boolean algebra relates to gates
see sum of products and products of sums,
if not good luck on that exam

[Anonymous No.7291654]

>>7291643
Thanks. I see it now.

[Anonymous No.7291674]

>>7285856
Determining the stability of nuclei involves calculations of the residual strong force, something I'm not familiar with. As for stability of an ion in a vacuum, you could probably calculate the energy of that ion relative to the energy of a system where the ion has lost one electron and that electron is moving in free space at infinite distance.

[Anonymous No.7291676]

>>7287400
Electrons move many many times faster than nuclei.

[Anonymous No.7291681]

>A car with 45 cm diameter wheels is accelerating from rest at 7.00 m/s2 on a horizontal road. After 3.00 seconds, the car runs over a poor, unfortunate bug that gets stuck to the bottom of the tire and then begins to rotate with it. What is the magnitude of the total acceleration acting on the bug immediately after it gets stuck and after two more seconds?

Is this just asking for the wheel's tangential velocity at 21m/s and 35m/s linear velocity?

[Anonymous No.7291682]

>>7289487
I twitch whenever someone tries to define entropy as "a measure of how disordered the system is"

Fuck you, just say S = k ln W

[Anonymous No.7291686]

>>7291607
Pretty much. There isn't really a better way to keep two sheets of stuff apart that want to blow up when they touch each other.

[Anonymous No.7291688]

>>7291682
>Using S = k ln W
Triggered


ΔS = ΔG+ΔH/T

[Anonymous No.7291695]

>>7291681

No, it's asking for is acceleration.

[Anonymous No.7291716]

>>7291688
If you want to use the classical thermodynamic definition, at least use dQ/T

[Anonymous No.7291744]

Where does vacuum permittivity come from? I can understand intuitively that charge density decreases as photons move away from source because they're spread over a larger area, and that the surface area of a sphere is <span class="math">4/piR^{2}[/spoiler], giving:

<span class="math">E = /frac{Q}{4 /pi R^{2}}[/spoiler]

As there's nothing in a vacuum to impede the motion of photons, how could the actual electric field strength be anything different? What's happening to the force carriers? More generally, even if there is a charged medium in the way, surely this would simply deflect a % of the photons, resulting in a dimensionless constant being added. Why does permittivity have units?

[Anonymous No.7291748]

>>7291744
Well, fuck. Make that second equation

Q
------------
4*pi*R^2

[Anonymous No.7291809]

This is mostly a problem with semantics.

Does the word "discontinuity" mean that the limit of a function does not exist?

[Anonymous No.7291830]

is the antiderivative of tan x the function of a semi-circle?

[Anonymous No.7291833]

>>7291830
I meant tan x+90

[Anonymous No.7291909]

Can we talk about GREs? How much and what type of preparation did you put in (general and subject -- mine is math, specifically), and what do you wish you had known/done differently?

[Anonymous No.7291969]

>>7286935
>would run forever unless subject to an external force or to wear.
so every machine ever?

[Anonymous No.7291991]

I have issues regarding anxiety when taking exams.
My stomach hurt and I want to go to the toilet. Moreover, I keep sweating.
I don't know why it keeps happening to me even if I study the materials thoroughly and I was supposed to feel confident.
Sometimes I made really stupid mistakes and lost (a lot) points because of that.
Please help. I have taken exams for 18+ years and I'm still worried everytime.

[Anonymous No.7292009]

>>7291909

The GRE general is pretty much the same as the SATs, with easier math.

[Anonymous No.7292021]

>>7291744
>>7291748

What do you mean why does it have units? That's like asking why force and energy use different units. Because they're different things. And if you just take out permitivitty fob that equation, it's an equation for a different thing.

[Anonymous No.7292081]

>>7291991
Please help.
;_;

[Anonymous No.7292092]

>>7292081
go to a doctor and ask for anti-anxiety meds.

[Anonymous No.7292105]

>>7284872
I asked this elsewhere, but because my question is so hard to word, I'm struggling to get an answer.

Pic related, Given that this is a two-tailed test, why does it matter if you use => or =<? I fully understand that as the binomial distribution is not symmetrical and that P(X<=7) is not equal to 1-P(X>=7), the two will give different answers.

I also understand that as 7 is not in the rejection region, the conclusion given by >=7 is clearly correct.

So, I suppose the best way I can word this question is as follows "The question gives us a value of 7 to work with ("Seven of the 12 people said that they preferred blue"), and our hypotheses are:
H0: P=1/3
H1: P is not equal to 1/3.
So how do we know that the right thing to do is consider P(>=7), rather than anything to do with P(<=7)? "

Basically, I'm baffled as to how we go from "the data give us the number 7" to "use >=7", (but I fully understand that >=7 must be correct)

[Anonymous No.7292154]

>>7291830
>>7291833
pls respond this is important

[Anonymous No.7292156]

>>7292105
Because we need to check, whether 7 deviates that much from expected values, so we need to change our hypothesis. For this two-tail test, we should find out whether our value is in region with probability of 0.95. That's why we start from 7.
However, I don't understand you question, really. I guess this is S2, btw?

[Anonymous No.7292166]

Say you have a sphere of some metal connected at two points opposite each other to a dc power supply. How do the electrons on the edges(basically the regions far away from the path of least resistance) move? Would they align with the electric field produced in a similar way to the classic iron filings in a magnetic field?

[Anonymous No.7292187]

>>7292156
>However, I don't understand you question, really. I guess this is S2, btw?
Yeah, I'm resitting it from last year (try doing an S2 paper before you've done the C3 and C4 calculus that you need, you're fucked). Turns out that this is actually the only question they've ever asked that I don't understand, I even went and redone the 2014 paper yesterday in 37 minutes, only dropped 4 marks, which feels fucking fantastic.


What I'm really asking, is why can't we use <=7?

I can't stress enough that I know why >=7 is right, I just can't see why <=7 is wrong (though I do understand how we can explain this in terms of critical regions, it's mostly p value that are bothering me here).

[Anonymous No.7292189]

>>7292156
Also, on a whim. Hi, Will - how's Nottingham?

[Anonymous No.7292198]

>>7292166
>Would they align with the electric field produced in a similar way to the classic iron filings in a magnetic field?

Yeah.

[Anonymous No.7292252]

>>7292187
Well, I am not sure if I completely understand your issue, but I think that use of <= 7 penalised just due to the fact, that 7 is closer to upper boundary of the most possible outcomes, so testing for P(X<=7) will give us nothing, as this region also includes expected value.
They use two-tail questions senslessly, to check whether student understands, that you need to use 0.025 instead of 0.05.

[Anonymous No.7292255]

>>7292189
Suckz.

[Anonymous No.7292309]

>>7292252
>as this region also includes expected value.
That... actually kinda makes some sense.

[Anonymous No.7292368]

Math teacher gave me 0 credit for this but I'm failing to see what I did wrong?

[Anonymous No.7292383]

>>7292368
You wrote it all the wrong way round, it's suppose to read from top to bottom, not centre to right.

HINT: ROTATE THE FUCKING THING

[Anonymous No.7292401]

>>7292368

Fudge, showed up normal on my phone. Here's fixed image

[Anonymous No.7292415]

>>7292401
is (1a) a previous exercise?

[Anonymous No.7292418]

>>7292415
Its where we defined the sets A and B which I used for other answers and got full credit so I didn't define a bad set

[Anonymous No.7292453]

At what level of Math can I say that I'm out of the "baby" Math? I just passed Calculus II and Linear Algebra.

[Anonymous No.7292495]

I'm learning commutative algebra, and exact sequences are tripping me up. Does anyone here know of a good reference on the topic?

[Anonymous No.7292503]

would a charged particle in a constant electric field keep due to the field until it reaches almost the spotted of light?

[Anonymous No.7292525]

>>7292503
keep accelerating

[Anonymous No.7292532]

>>7292495

I was introduced to exact sequences through Atiyah Macdonald in ch. 2, although of the course the treatment is very sparse it was enough for me to get by for a while.

If you know some rudimentary category theory the first chapter of this book may help:

http://www.math.unam.mx/javier/weibel.pdf

For a while I just though exact sequences were a clever way of writing down quotient objects and I never really understood them until I actually had to use them in alg, topology and alg. geometry and I suspect that's the case for anyone who first learns the abstract defn first, so you may want to look into homology sequences or short exact sequences of sheaves in alg. geom or something if you happen to be interested in those fields.

[Anonymous No.7292544]

>>7292503
It would accelerate forever, getting ever closer to the speed of light, but never reaching it.

[Anonymous No.7292547]

>>7292401
I can't see where there's an error with how A is defined there

[Anonymous No.7292549]

>>7292453
Who cares? Whenever I learn more math I feel like what I learned was trivial (even if it wasn't) and move on.

[Anonymous No.7292554]

I'm a fuck up who got accepted to some ok universities for undergrad. The CC I go to is giving me shit registration dates so there's not much left I can do here. I'm transferring in as a junior and my question is if I want to prepare for grad school, how would I make up for the mediocre reputation from the uni I would get my bachelor's from?
24 year old EE major btw

[Anonymous No.7292619]

>>7292544
why would it accelerate forever even though the field it's constant?

[Anonymous No.7292630]

>>7292619
because Eq= F= ma?

[Anonymous No.7292647]

>>7292619
Because the field is constant, there is always a force on the particle.

>>7292630
Since the original question was about lightspeed, I should add that F = ma doesn't work at relativistic speeds, and <span class="math">d^2x/dt^2[/spoiler] will approach zero as you approach the speed of light, but never reach it. The relativistic version is <span class="math">F = dp/dt[/spoiler] where <span class="math">p = mv/\sqrt{1-v^2/c^2}[/spoiler]. F = qE still works.

[Anonymous No.7292678]

>>7284872
Does quality of education matter a lot in a computer science course? Or can you pull your own bootstraps?

[Anonymous No.7292805]

>>7292532
I'm learning it in order to tackle AG next semester, so I suppose I'll see some applications then. I'll check out Hatcher's homology section in the meantime though. Thanks.

[Anonymous No.7292818]

>>7292647
i if that is true, why do objects accelerate towards the earth at a constant rate? shouldn't the acceleration of the object keep increasing as it gets closer to the source of the gravitational field?

[Anonymous No.7292885]

>>7292818
>shouldn't the acceleration of the object keep increasing as it gets closer to the source of the gravitational field?

It does.

[Anonymous No.7292929]

>>7292885
you're talking about the rate of change of the rate of change of the speed right? the d3x/dt3

[Anonymous No.7292962]

>>7292929
Yes. Of course, for a typical falling object, this effect is very small, and dwarfed by air resistance, which makes the acceleration decrease as the object falls faster.

[Anonymous No.7292979]

>>7292962
thank you for confirming my thoughtd

another question: If a charged particle is accelerated, will it eventually lose its acceleration to the electromagnetic waves itproduces and go back to its initial velocity?

[Anonymous No.7293023]

>>7292979
You mean if you accelerate it for a while and then just let it move in a straight line? It will give off radiation while you're accelerating it, but not after you stop.

[Anonymous No.7293049]

So.. what exactly is this (co)homology nonsense and why should I care as a prospective algebraist ?

[Anonymous No.7293061]

>>7292647
It works fine. You're just using it wrong.

What I want to know is what happens to the electric field at those speeds.
Doesn't relativity change electric fields into magnetic fields?

[Anonymous No.7293152]

>>7293061
>It works fine. You're just using it wrong.
If you mean F = ma is true in the rest frame of the particle, that's correct.

>What I want to know is what happens to the electric field at those speeds.
>Doesn't relativity change electric fields into magnetic fields?
Not if the motion is in the same direction as the electric field. In that case the field is unchanged under the Lorentz transformation.

[Anonymous No.7293153]

So, regarding compactness, a set is compact if it can always be made from a finite subset of its covers? Maybe I'm not understanding this right, but I don't exactly see what this is supposed to entail.

[Anonymous No.7293172]

how do I get good at calculus II?

I barely scraped by in calculus 1 with a low C. I don't want the same to happen for calculus II, I need an A. So I'm planning on studying this summer to be "ahead" or just be able to understand my professor's better.

Can anybody recommend a good textbook to practice that (you) have used? I know the wiki has textbooks, but how I do know which ones are legit?

i already have schaums btw, but I want something to teach me how to do it.

[Anonymous No.7293178]

>>7293153
It's supposed to give a notion of finiteness in topological spaces. I can't get the link to copy right, but if you Google "terry tao compactness" he has a short and enlightening expository paper on this.

[Anonymous No.7293792]

I live in California and currently looking at the UC schools. In UC Davis, they offer concentrations for CE. I find networks and robotics interesting. Do other UCs offer the same thing? I looked at their page and didn't see anything like on UCSC assist page.

[Anonymous No.7294015]

>>7293061
>It works fine. You're just using it wrong.
If you mean F = ma is true in the rest frame of the particle, that's correct.

>What I want to know is what happens to the electric field at those speeds.
>Doesn't relativity change electric fields into magnetic fields?
Not if the motion is in the same direction as the electric field. In that case the field is unchanged under the Lorentz transformation.

[Anonymous No.7294049]

why do photons have momentum\

[Anonymous No.7294065]

>>7294049
If you mean why they have momentum when they have no mass, in special relativity momentum is not mass times velocity but <span class="math">E/c^2[/spoiler] times velocity.

[Anonymous No.7294091]

>>7294065
so, the momentum of light is proportional to its frequency?

[Anonymous No.7294102]

>>7294091
Assuming light in a vacuum, yes.

[Anonymous No.7294103]

>>7294102
*the momentum of a photon, specifically.

[Anonymous No.7294107]

>>7294102
why isn't the momentum equal to the momentum of the particle that emitted the photon divided by 4/3*pi*r^3?

[Anonymous No.7294110]

>>7294107
I'm not sure why you think it would be.

[Anonymous No.7294128]

>>7294110
I'm not sure either, I just assumed than photons were points in electromagnetic waves

[Anonymous No.7294133]

>>7294128
Photons are energy levels of electromagnetic waves. In the same way an electron in an atom can only have certain energies, waves in the electromagnetic field can only have certain energies.

[Anonymous No.7294139]

>>7294133
>waves in the electromagnetic field can only have certain energies.
does this mean em waves are pulses and not sine waves?

[Anonymous No.7294145]

>>7294139
If you add together different sine waves, you can get pretty much any waveform you want.

https://en.wikipedia.org/wiki/Fourier_transform

[Anonymous No.7294149]

>>7294145
what do you mean? can you give an example

[Anonymous No.7294160]

>>7294149
any waveform
https://www.youtube.com/watch?v=NAsM30MAHLg

[Anonymous No.7294184]

>>7284992
You're on /sci/ and everyone one here jerks off to Spivak or Stewart.

[Anonymous No.7294211]

is spin the same as te magnetic moment of a particle?

[Anonymous No.7294223]

if you isolate a single oxygen atom and 'put' an electron near the atom, would it attract the electron? If so, what force would attract the electron(I'm guessing it's magnetism)?

[Anonymous No.7294225]

>>7294149
This is a nice explanation:
http://web.archive.org/web/20140216135454/http://www.altdevblogaday.com/2011/05/17/understanding-the-fourier-transform
http://dave.whipp.name/tutorial/fourier.html

[Anonymous No.7294231]

Anybody can help me with this? I came to a conclusion that differs from the book's. Regarding the point K, to me it is obvious there are 2 normal tensions acting, one due to the 15kN and other due to bending t=-My/I, and they are acting in opposite directions, the one due to bending is tensioning and the one due to force is compressing.

The book says the two are in the same direction. Which is right?

[Anonymous No.7294753]

fucking bump

[Anonymous No.7294802]

>>7284872

X/3(10) = 0

What do I do to get rid of the /3?

[Anonymous No.7294844]

I have a nephew who goes to high school. It's been a while since I've been to school, but do students do anything on the last week of school?

[Anonymous No.7295242]

Extremely retarded question here, pls no bully

As a pleb I haven't done anything math related for a long time, and I am trying to simplify:

xy^2(x^2 + y^2) - 3(2xy^2 - 2xy^3) + 2y^2(x - xy^2 - x^2)

I am able to distribute just fine:

x^3y^4 + xy^4 - 6x^2y^2 + 6x^2y^3 + 2xy^2 - 2xy^4 - 2xy^2

However, after combining like terms, I end up with a differently ordered expression from the one symbolab gives of:

x^3y^2 + 6x^2y^3 - 8xy^2 - xy^4 + 2xy^2

I can't figure why the hell the expression is ordered in this way, even after reviewing videos, and the condensed step by step solution. Throughout the step by step solution, they move things around, and I am baffled as to why, even though I am sure there is an incredibly simple reason.

pls help

symbolab breakdown (https://www.symbolab.com/solver/step-by-step/xy%5E%7B2%7D%5Cleft%28x%5E%7B2%7D%2By%5E%7B2%7D%5Cright%29-3x%5Cleft%282xy%5E%7B2%7D-2xy%5E%7B3%7D%5Cright%29%2B2y%5E%7B2%7D%5Cleft%28x-xy%5E%7B2%7D-x%5E%7B2%7D%5Cright%29/?origin=button))

[Anonymous No.7295270]

>>7295242
Well judging by your first term I already see a mistake
>xy^2 * x^2 = x^3y^2
Not x^3y^4

[Anonymous No.7295283]

>>7295270
Fuck it I'll do the whole thing. You didn't distribute properly in some places.

x^3y^2 + xy^4 - 6xy^2 + 6xy^3 + 2xy^2 - 2xy^4 - 2x^2y^2

[Anonymous No.7295294]

>>7295283
Simplified this becomes x^3y^2 - 2x^2 y^2 -xy^4+ 6xy^3 - 4xy^2

So I guess you did some mistake either when writing the expression here or in symbolab.

[Anonymous No.7295298]

>>7295270
>>7295294
Sorry, my mistake. I am fucking idiot and missed two typos .

x^3y^4 was a typo. x^3y^2 is what I have down on paper.

And in the problem, - 3(2xy^2 - 2xy^3) should have been:

- 3x(2xy^2 - 2xy^3)

Thus the correct problem was:

xy^2(x^2 + y^2) - 3x(2xy^2 - 2xy^3) + 2y^2(x - xy^2 - x^2)

And distributed to:

x^3y^2 + xy^4 - 6x^2y^2 + 6x^2y^3 + 2xy^2 - 2xy^4 - 2xy^2

[Anonymous No.7295306]

>>7295298
Alright, then the mistake is in your last term. Should be -2x^2y^2.

[Anonymous No.7295315]

>>7295306
So your symbolab solution is correct, except for the third term which I suspect is a typo (should be -8x^2y^2).

[Anonymous No.7295339]

how bad is it to fail a 2nd year maths unit? i passed all my first year units and haven't failed anything yet at uni but i'm worried this is really going to hamper my chance of getting into the honours year, and if i fail this it means i'll have to retake it in a year's time (as opposed to in summer/winter school or next semester)

is my best chance to try and gun my other 3 subjects?

[Anonymous No.7295341]

>>7295306
>>7295315

Fucking christ, I missed that that typo too. I am not used to reading and typing algebra this way. It makes it hard to read and double check for me.

Ok, for the last time, the correct distribution:

x^3y^2 + xy^4 - 6x^2y^2 + 6x^2y^3 + 2xy^2 - 2xy^4 - 2x^2y^2

Now, when it comes to combining like terms, I know that - 2xy^4 and xy^4 are similar, and that subtracting gives you -xy^4.

The second pair of like terms are -6x^2y^2 and -2x^2y^2. When subtracted, they are -8x^2y^2

The problem is, I how to correctly place them. Like I said, I understand why the coefficients, variables, and exponents simplify to what they are, I just understand how symbolab arrived at that order.

Because I end up with the obviously wrong expression of x^3y^2 - xy^4 + 6x^2y^3 - 8x^2y^2 + 2xy^2.

Is the issue something to do with order of exponents?

[Anonymous No.7295347]

>>7295306
>>7295315

Fucking christ, I missed that that typo too. I am not used to reading and typing algebra this way. It makes it hard to read and double check for me.

Ok, for the last time, the correct distribution:

x^3y^2 + xy^4 - 6x^2y^2 + 6x^2y^3 + 2xy^2 - 2xy^4 - 2x^2y^2

Now, when it comes to combining like terms, I know that - 2xy^4 and xy^4 are similar, and that subtracting gives you -xy^4.

The second pair of like terms are -6x^2y^2 and -2x^2y^2. When subtracted, they are -8x^2y^2

The problem is, I don't know how to correctly place them. Like I said, I understand why the coefficients, variables, and exponents simplify to what they are, I just don't understand how symbolab arrived at that order.

Because I end up with the obviously wrong expression of x^3y^2 - xy^4 + 6x^2y^3 - 8x^2y^2 + 2xy^2.

Is the issue something to do with order of exponents?

[Anonymous No.7295488]

If my high school american freshman cousin who just finished geometry wants to get right into the algebra necessary for precalculus, what are some good, free resources for learning over the summer?

[Anonymous No.7295643]

>>7284872

What are some good books on series at a beginner level? To be more precise I want to be an absolute genius on Cauchy sequences and all the theory behind them.

[Anonymous No.7295894]

>>7295347
>obviously wrong expression

Lolwut? It's correct. The ordering doesn't matter.

[Anonymous No.7296033]

>>7294223
resbond pls

[Anonymous No.7296205]

i have this expression on my book and i'm too retarded to understand it. an electron is travelling on a circular orbit, and the intensity of the current that it produces is

i = dq / dt = (dq/dr)(dr/dt) = (-e / 2*pi*r)*v

why the fuck does dq/dr = (-e / 2*pi*r)?

[Anonymous No.7296269]

How much current and voltage does a short circuit conduct?

[Anonymous No.7296275]

>>7296269
R=0 so it theoretically conducts infinite current

the voltage conducted is 100%

[Anonymous No.7296292]

>>7296269
>>7296275

A short circuit is just two points in a circuit that are connected with zero resistance (i.e. a "wire"), in parallel with the load (and thus bypassing it). So the two connected points will have the same voltage ("conduct voltage" doesn't really make sense as a phrase) and will conduct whatever current makes sense in that situation - generally a lot more than is intended.

It would only have "infinite current" if you were shorting the two ends of an ideal voltage source, but that's impossible. A voltage source is always in series with a resistor in circuit diagrams, representing its internal resistance.

[Anonymous No.7296312]

>>7296275
>>7296292
and what's the maximum amount of current of copper can take without 'damaging' its lattice?

[Anonymous No.7296433]

>>7296312
Resistive heating is what causes the damage. The wire isn't the problem, cause all that does is heat up until it melts. The problem is that you usually have lots of stuff around the wires that you don't want getting hot, because they either melt or catch fire. Exactly how much current you can safely pass depends on the properties of the wire itself.

[Anonymous No.7296435]

>>7296433
how hot can the wire get when shorting?

[Anonymous No.7296442]

The warpdrive is a scam right?

[Anonymous No.7296443]

>>7296435
Depending on the resistance of the wire, hot enough to melt. Fuses are basically that.

[Anonymous No.7296455]

>>7296443
let's say 1mm diameter, 6cm long wire connected to a 120V source. What would be its temperature? Would it evaporate? How hot does it have to be to stop conducting current?

[Anonymous No.7296464]

>>7296455
also, will the parts of the wire closer to the ends of the source heat up faster or slower than the points in the middle of the wire? I'm guessing not

[Moose No.7296513]

>>7296464
Depends upon the particulars.
Typically there is a slightly higher resistance at the joints and the more heating, but this can be offset by a larger surface area.

>>7296455
120 AC or DC?
What is the wire made of?
Is it single or multi- strand?
What is the ambient temperature?

[Anonymous No.7296524]

>>7296513
DC
Copper
does it matter?
~30C

>Typically there is a slightly higher resistance at the joints
why? how do we analyze this?

[Anonymous No.7296533]

>>7296455
Not that guy.

>Would it evaporate?
No.

You should really have a timescale as well.

When it's melted so that the circuit is broken, it won't conduct.

[Anonymous No.7296549]

>>7296533
would it evaporate at a higher voltage?

[Anonymous No.7296555]

This really is a stupid question. To statisticians or people involved in such studies:

Is there data available about how many times do couples have sex daily and how long the time between?

I think there should be some average data for comparison.

[Moose No.7296558]

>>7296524
I'm going to be lazy and not calculate this out, but yes it would melt very quickly.

>does it matter?
Multi-strand conducts AC better.

[Anonymous No.7296576]

Where does the Rydberg constant come from? How was it derived?

[Anonymous No.7296580]

>>7296558
>Multi-strand conducts AC better.
what's the difference?

[Anonymous No.7296591]

>>7296576
Literally Google.

[Anonymous No.7296599]

>>7296580
If it conducts it better, it probably has lower resistance and therefore will heat up slower/less than single strand.

Assuming you're the same guy, you need an extremely high amount of energy to make metal evaporate. Over 2000 degrees Celsius for most metals (~350 for mercury).

[Anonymous No.7296606]

>>7296205
guys halp

[Anonymous No.7296616]

>>7296205
what book and topic is this?

[Anonymous No.7296625]

>>7296599
>If it conducts it better, it probably has lower resistance and therefore will heat up slower/less than single strand
what makes it physically different than a single stranded wire with the same diameter?

[Anonymous No.7296682]

how do you determine the frequency of an electron the is constantly accelerating in 1 direction?

[Anonymous No.7296687]

>>7296625
current is carried on the surface of conductors. more strands = more surface area to conduct charge

[Anonymous No.7296693]

The outcomes of the roulette wheel itself are completely random, meaning every outcome has equal probability. The payouts are calibrated to favor the house. There are 36 red/black numbers and two green (0 and 00) for a total of 38 outcomes. A payout for a single number is only 35 to 1 or $36 for a $1 bet (you get your $1 back so $35 + $1 = $36). This give the house a 2/38 = 5.3% edge over players.

[Anonymous No.7296697]

>>7296687
>current is carried on the surface of conductors
what the fuck; I didn't know that

sauce?

[Anonymous No.7296706]

>>7296697
A charge will always be on the circumference of a disk. A wire is like lots of disks

[Anonymous No.7296713]

I'm taking Calculus III in the fall semester. Anyone know what level is that in high school?

[Anonymous No.7296717]

>>7296706
is it impossible for a charge to be at the middle of the disk?

[Anonymous No.7296722]

>>7296717
Yes, as the electric field inside the ring of charges must be 0.

[Anonymous No.7296729]

suppose you have 2 charged particles at a distance r apart and both particles are accelerating at the same rate, would there be a magnetic attraction between the particles? How fast should the particles be going for the magnetic force between to cancel out the electrostatic repulsion between the particles?

[Anonymous No.7296732]

>>7296722
why do the charges disperse to the perimeter or surface of a conductor?

[Anonymous No.7296736]

>>7296732
>>7296722
what's the math behind this?

[Anonymous No.7296741]

An example may help. Deal out cards consecutively (without replacement) from a standard 52 card deck. A success is a black card a failure a red card. The first card has a 26/52 = 1/2 chance of success. The second result depends on the result of the first card and success is either 25/51 or 26/51. Hence dealing cards without replacement cannot follow a binomial distribution.

[Anonymous No.7296805]

What can I do with an associates in Math?

[Anonymous No.7296848]

>>7296805
Suck SnanS and eat qoc

[Anonymous No.7296857]

>>7296616
book isn't in english

the topic is quantum numbers in the bohr atom

but really I don't understand only that calculation

[Anonymous No.7296867]

>>7296805

You can probably tutor elementary students.

[Anonymous No.7297091]

What about subjective experience?What is neurobiology think about it?What are you opinion?

[Anonymous No.7297147]

just out of curiosity, what do particle physicists actually do with these shenanigans?!

[Anonymous No.7297175]

>>7296687
>current is carried on the surface of conductors
>>7296625
>>7296697
>>7296706
>>7296717
>>7296722
>>7296732
>>7296736

No it isn't. Current is carried through the whole conductor. That's why conductance is proportional to cross section, not perimeter. When wires are multiple strands it is because they are more flexible that way. (Or they are actually separate wires.)

Anon is probably mixed up because STATIC charge is always at the surface of a conductor. And the reason for that is simply because like charges repel - if there are charges in the interior, they can spread out more, so they do.

[Anonymous No.7297477]

>>7297175
>No it isn't.
True for DC. Look up the skin effect for AC current.

>STATIC charge is always at the surface of a conductor
You mean excess charge, right?

[Anonymous No.7297484]

>>7297147
Learn for yourself...
http://theoreticalminimum.com/courses/particle-physics-1-basic-concepts/2009/fall
http://theoreticalminimum.com/courses/particle-physics-2-standard-model/2010/winter
http://theoreticalminimum.com/courses/particle-physics-3-supersymmetry-and-grand-unification/2010/spring

[Anonymous No.7297570]

My commutative algebra text had decided to assume familiarity with the tor functor. Can anyone point me towards a concise exposition of it?

[Anonymous No.7297574]

~~~~~~~~~~WHICEVER FUCCBOI MAKES THESE NEW THREADS~~~~~~~~~~
could you please link the new thread when you make a new one? kthxbai

[Anonymous No.7297575]

According to back-then school physics gravity is transmitted via curved spacetime

How is (electro)magnetism transmitting forces?

Gravity curves space, hence objects are moving towards each other

Anything similar with magnetism?

[Anonymous No.7297607]

>>7297575
Photon interaction