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Page: 1 2 3 4
Comments:
<0> re
<1> hi
<2> hi...
<2> I have to do some task for my physics course at school...
<2> and there is given the half-life period of a certain kind of radium in the task...
<2> it is 1600a
<2> what does "a" mean?
<2> years?
<3> joerg, not sure
<3> charging a chain of batteries (series), is there any theoretical reason why the end batteries should be more heavily loaded than the others? it seems to be the case in practice
<2> DanF_DrC: a is for years ;)
<2> DanF_DrC: found it in the german version of wikipedia :)
<3> joerg, what language is your data?
<2> DanF_DrC: german...
<2> DanF_DrC: but annus (year) is latin :P
<3> joerg, how old was the text book?
<2> DanF_DrC: 1998
<4> Heyyy
<4> What does an electric field *do*?
<2> nothing
<2> its just there
<4> then how are we able to ascertain its existence?
<5> it affects charges in a predictable way
<4> that's like saying that there are such things as fairies, but they don't do anything; but if they don't do anything we can't then tell whether or not they are there (they would have to say, bounce photons out towards you when you look in their direction, that way we can see them, or something like that)
<4> hm
<4> How does it affect said charges ?
<5> it accelerates them
<5> E = F/q and Fnet/m = a
<4> So if I have some polyelectron atom that is in ground state, and put it into the visicinity of an electrical field, the electrons will will suddenly get into an excited state?
<5> not necessarily
<5> I don't know what effect electric fields have on electron orbitals
<4> Hrm, then what do you know? gimme example, please?
<5> what do I know about what?
<4> Well, you're saying that my example was not exactly correct
<4> and I think you're being honest there
<6> microacg: electric fields
<4> but what other situations are there?
<4> That you would be able to explain the influence of the electrical field?
<6> kanzure: you mess up force and energy
<4> Other than the one I presented (which has already been established as likely incorrect)?
<4> How does it mess up 'force' and energy?
<6> ground states are about energy
<5> suppose you isolate a proton
<5> and hold it in place
<6> while the E-field excerts a force
<4> alright, in some sort of chamber?
<5> it creates an electric field with lines that go out radially in all directions, and decay like 1/r^2
<4> Oh?
<5> now place an electron some distance away from the proton
<4> What do we call this electric field, just "the proton's electrical field" ?
<5> I suppose
<5> the electron is attracted to the proton, thus, the electron will accelerate towards the proton
<5> this is the cl***ical explanation of a hydrogen atom
<5> (not terribly accurate but good for understanding electric fields)
<6> kanzure there are 2 fields the electrons field and the protons field
<4> hmm
<6> both fields add up
<4> so this field, then, what can it be imagined as?
<5> Manyfold: I insisted that the proton is held in place so the field of the electron isn't that important
<4> Just this "range" under which the electron is under the influence of the proton?
<6> this is called superposition
<5> kanzure: I'll link you to a picture of the electric field of a stationary proton
<4> excellent
<5> http://www.physics.miami.edu/~zuo/cl***/fall_05/supplement/Figure21_16.jpg
<7> http://tinyurl.com/y2lejr
<5> notice the further points have shorter arrows
<5> but they all point away from the proton
<4> So what are these points?
<6> kanzure the E-field is a vector field which means it ***icotes a vector with every point of space
<5> they are random points
<5> they have no significant meaning
<5> as Manyfold put it
<4> Hmm
<4> Vector fields, I haven't worked with those yet
<4> has it something to do with vector calculus?
<5> it does
<5> but you don't need to think about it that way for simple electric fields
<6> kanzure: yes a lot
<4> At one of these points, then, the electron, correct?
<4> (The electron is at one of those points?)
<6> microacg: so how should he think about it?
<5> It's hard to help him think about it at a basic level over irc
<5> kanzure the electron can be anywhere
<5> the electric field says what force that electron will experience it, depending on where you place it
<4> Right, and for the point or location that the electron *is* at, there is a vector at that point as well, yes?
<6> as our field fills all space
<5> kanzure: yes
<5> however, electric field gets really small if you go very far away, so the electron won't really be affected if r is very large (you can tell this is I said the field decays like 1/r^2)
<5> if you get really close the field is huge so you try to avoid that
<4> interesting
<8> electrons are like really small chickens aren't they ?
<4> They walk around a lot?
<6> boring
<8> only if you decapitate their heads kanzure :P
<4> My mistake, I really have to study up on my interstellar chicken astrophysics
<5> lool
<8> indeed :P
<6> kanzure: you really must start to work with mathematical expressions and stop relying on pictures alone if you want to become a real scientist
<6> so F=ma , E=F/q
<8> feynman might disagree there :P
<4> Manyfold: Hey, nobody told me what an electrical field was in terms of 3D space, which is what I encounter the world in. If somebody was to spit it out, ...
<4> Feynman does disagree completely
<8> i think he would claim that pictures are mathematical expressions
<4> And I seem to be taken up by his explanations much more frequently
<8> except for the fact that he is dead :P
<4> They are, they are!
<4> bah, dead
<6> ?
<8> well it's all just a part of life you know :P
<4> hold on
<4> looking up anecdote
<4> "Feynman's last anecdote", it is called
<6> kanzure: the E-field puts to every point of space an vector
<4> still searching
<4> `The last Feynman story of them all goes something like this. Gweneth was by his beside in the hospital and Feynman was in a coma. She noticed that his hand was moving as if he wanted to hold hands with Gweneth. She asked the doctor if this was possible but was told that
<4> the motion was automatic and did not mean anything. At which point, Feynman, who had been in a coma for a day and a half or so, picked up his hands, shook out his sleeves and folded his hands behind his head.
<4> It was Feynman's way of telling the doctor that even in a coma he could hear and think - and that you should always distrust what so-called 'experts' tell you!`
<4> Death, bah
<4> (from Lectures on Computation, Feynman)
<4> Feynman's what you get when you read to your child from the encyclopedia
<9> Feynman ftw
<6> ftw?
<10> for the win
<11> kanzure: http://physnet.org/home/modules/pdf_modules/m120.pdf Chapter 3 pg 5 & 6
<6> what are input and output skills?
<11> Dunno. Looks like it was set up as a lesson plan.
<5> ROYGBIV
<4> xtmdster: Thanks for the linkage
<5> why is it that sometimes when washing my face with hot water the water feels cool to my hands while my face find the water scalding, and other times my hands can barely stand the water yet my face doesn't mind it?
<12> wow - is the National Physical Science Consortium website hacked ?
<0> morning
<13> hello
<14> hi #physics !
<8> hi _chill !
<15> wow, a physics channel on freenode
<15> didn't know it existed
<16> All of the cool channels are here
<16> #electronics, #physics, #asm, #etc. :)
<15> funny, I'm on #asm on efnet too :)
<0> re
<17> Topic locks are for lame channels.
<3> what did you want to change it to?
<17> Change what to? I was refering to the no +t, meaning anyone can change the topic.
<3> maybe
<18> Whats the speed up to which one in general uses cl***ical formulas? which percentage of c?
<3> expose, magnetism is a relativistic effect so it can manifest at very low speeds. but for normal eartbound motion and mechanics relativity is completely ignored
<3> radar gun for cars can use relativity though
<3> same with doppler radar for aircraft
<18> DanF_DrC: well, if i have the kinetic energy and the cl***ical formula 1/2*m*v^2 the resulting speed wont be exact for high enough energies.
<18> or, vice versa the energy wont be "exact enough", and i wanted to know from which point on one typically uses the relativistic way of calculating the values...
<3> it's a smooth transition. I think 90% of C is a distortion of about a factor 2. if you stay below 1% of C you are fairly accurate but only on certain matters like kinetic energy
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