/sci/ - Science & Math

>>7449330
the same way as fission but opposite pretty much.

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

http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/nucbin.html

>>7449350
Yeah that makes no sense, that would mean you lose energy.

>>7449330
isn't it because when 2 protons collide and fuse together (in the sun for example), one of the protons decays into a neutron due to the instability of the molecule and some of the mass is lost in the form of energy, and because of the energy-mass equivalence (E=mc^2) a small amount of mass contains a very large amount of energy, so the energy comes from the conversion of mass into energy.
someone correct me if i'm wrong i just browse the internet for information lol

>>7449368
>that would mean you lose energy
no

>>7449371
Fuck off you useless shitposter.

>>7449370
>protons decays into a neutron
wut

>>7449368
No, actually, it wouldn't.

A good way to think of it is that stuff releases energy by moving to a more stable, low-energy state. Atoms in the vicinity of Iron and Nickel are the most efficient, lowest-energy way to arrange protons and neutrons.

Anything that brings atoms closer to iron - whether it's fusing light atoms into less light atoms or fizzing really heavy atoms into less heavy atoms - releases energy.

>>7449370
Yeah I was thinking about that equation and wondered where c comes into play.
If it is as I said, the neutron carries the energy. Then it has to shoot out very fast. But it can't travel at light speed. So, I don't get it.

>>7449330
Things like being stuck together. When you put things together the universe rewards you with energy. The problem is that there are other pesky forces in the way of sticking the things together that must be overcome. But once you do you'll be rolling in the energy.

>>7449382
Holy shit, I was answering the post. I'm not saying fusion takes away energy.

>>7449384
No offense but it doesn't sound like you have a very complete understanding of it.

>The universe likes it so u get energy.

>>7449387
welcome to classical thermodynamics my friend.

To put it in this way.
Energy has to have a form. So my question is in which way does the energy from fusion come?

>>7449383
Your explanation is 100% wrong. The answer lies in this graph:

>>7449371

This shows a chart of binding energy per nucleon (protons and neutrons). The higher the binding energy, the more tightly the nucleons are bound. Moving from atoms with low binding energy per nucleon to ones with high binding energy per nucleon is like letting magnets pull together or letting raised weights fall - it releases energy.

So basically, anything which moves up the slope of that chart produces energy. As you can see on the right, going from Uranium to ligher atoms produces energy. And as you can see on the left, going from really light atoms like hydrogen or helium to heavy atoms produces energy.

E=mc2 comes into this because the extra energy involved in binding nucleons into an atom manifests as extra mass, and this mass is converted to energy when transforming to atoms with less mass per nucleon,

>>7449376
>muh shitposting

>>7449396
>muh
>doesn't understand the meaning of the words he use
Is your image supposed to mean something?

>>7449378
through the process of beta decay. 2 protons fused together is a highly unstable system so one of the protons ejects energy and a positron (antimatter, an electron with a positive charge) and turns into a neutron.
https://en.wikipedia.org/wiki/Beta_decay#.CE.B2.2B_decay

>>7449383
im sure someone could explain how exactly c comes into play in the reaction system but unfortunately i have no idea. im trying to interpret what is on wikipedia but i am not well versed in particle physics or mathematics for that matter.

>>7449404
it means you dont know what youre talking about

>>7449393
Imagine you have two separated magnets. If you release them and let them pull together, this will release energy; there's potential energy stored in their separation.

Nucleons in atoms are stuck together with a very strong force called the Strong Force. If you give hydrogen atoms a chance to stick together into helium atoms, this will release energy just like letting those magnets slam together released energy. (Because E = mc2, these energy differences manifest as mass differences.)

Once you get past a certain number of nucleons in an atom, the Strong Force stops holding them together so well and they get a little unstable; the protons on one end are too far away to attract the protons on the other. If you split these heavy atoms into two smaller globs that can attract each other better, this will also release energy, because the smaller clumps are more energetically favorable.

The crosover spot between these two - where building up bigger atoms stops being profitable, and splitting smaller atoms stops being profitable - is around the element iron.

>>7449393
the energy comes from the binding energy, but it comes in the form of kinetic energy of the products (and occasionally gammas)

>>7449404
It's Binding energy/nucleon, if you don't know what that is refrain from posting ITT.
Just google binding energy/nucleon for a start.

>>7449408
I don't know fusion fysics. I know what I'm talking about though, and I know shitposting when I see it.
>Faggot thinks some credentials means he isn't shitposting
Fuck off, dumbass.

>>7449416
>posting a correct response to an incorrect assumption is shitposting
am i being rused m8

>>7449417
>fysics
what do you think m8

>>7449406
Oh shit. Splitting of protons.
>I learnt something

>protons ejects energy
something doesn't jive with this. Do you understand what energy is?
A lot of people seem to have a bad understanding of energy and think energy actually "is something" in the universe.

>>7449417
>having this severe autism
My point was that a simple no is a completely useless shit answer that doesn't explain anything.

>>7449423
did you completely ignore the picture, or the other two links i'd posted before that? get your head out of your ass

>>7449426
If you know what you're actually talking about it should be a simple task to answer if the energy comes from the released neutron or not. That would be a yes/no answer I could accept. Although I would appreciate more information after that.

>>7449428
explained that already. it doesnt come from the neutron, it comes from the binding energy, and is carried by the fusion products in the form of kinetic energy

>>7449420
"energy" in physics terms is typically kinetic which simply means its in motion but can mean heat or light emission

>>7449420
energy is the ability to do work

>>7449429
>Binding energy
Obviously it comes from the binding fields, I was wondering what the fusion products are that carries the energy. And the neutron is part of that btw.

>>7449433
https://en.wikipedia.org/wiki/Fusion_power

http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/fusion.html

>>7449433
I'm guessing it's heat, just like in fission.

t.armchair expert

>>7449433
each fusion product carries some of the energy, based on momentum conservation, and sometimes there are gammas, like with D-T, 1 in 1000 or so reactions

http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/fusion.html

>>7449433
Depends on the reaction. Generally some combination of the kinetic energy of the product nucleus, photons, and the kinetic energy of either protons, neutrons, or both released as side products.

For instance, the D-D reaction has a 50% chance of emitting a T (1.01 MeV) and a proton (3.02 MeV), and a 50% chance of emitting helium-3, (0.82 MeV) and a neutron (2.45 MeV).

>>7449437
>heat
>subatomic particles can be hot or cold

>>7449444
i dont think you understand what heat is. it's literally energy transfer

>>7449446
nope, it's not that simple.

>>7449444
do subatomic particles not have energy, or?
explain

>>7449447
it literally is

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

>>7449449
>A ball becomes hot when you lift it

>>7449420
what i meant was what >>7449430
said
i understand what energy is, but like you said energy isn't actually "something" and i dont quite understand what that actually means. forgive me for my brain is hungry for knowledge but its power is weak.

>>7449463
because scientific terms, and indeed all words, are self-referential.
energy is defined as the ability to do work
you won't find an answer in science as to what energy really "is", because it's a basic property of the universe and our human senses cannot perceive it intuitively
take light for instance, it is neither a particle nor a wave, but that's how we've come to understand it

t.notanexpert

>>7449463
He just meant that energy isn't a substance; you can't have a reaction or something just throw out "energy." "pure energy" is not a thing.

Things *have* energy. Energy is not a thing separate from other things.

>>7449463
You're a good person I sense and you know you don't necessarily understand the fundamentals unlike the "I have a degree and I know everything and you don't, here's a graph that doesn't explain anything about what you just asked."-people.
Good luck in your search for knowledge.

>>7449371
>>7449395
Okay I'm confused. How can you gain energy by going from a low energy state to a high energy state. Wouldn't it be completely opposite? Wouldn't you have to add energy to go to a higher energy state? What am I missing?

>>7449368
Fusion and fission can both result in a net loss or a net gain of energy. In the case of nuclear power plants, unstable isotopes decay and release energy, and in a hypothetical fusion plant, less stable isotopes are fused into more stable isotopes. That transition, unstable -> stable, is the basis of basically any form of energy production.

ITT: /sci/ fails at teaching again

>>7449376
>I can't figure out a graph and want to be spoon fed

>>7449384
question was answered less than 10 posts in.

OKAY THEN, ANSWER THIS QUESTION.

If two nuclei need energy to fuse and hold together then were does the gain in energy come from and why?

>>7449641
Are you fucking kidding me you retarded faggot? Graph says nothing to answer the question.

>>7449672

The same way you get more energy than you spend by stuffing your mouth full of duck

>>7449688
how do the nucleii digest the duck?

Jesus Chirst just answer the fucking question straight forward.

Where does the energy come from?

>>7449396
Holy shit, you got an A in Choi's class?

>>7449682
no, but the links above it combined with the graph do.

>>7449416
Get a load of this faggot

>>7449709
Pfft. The answer has been given many times in this thread.

It seems that in order to understand your own question AND the answer, you need to learn more about physics.

Or you're a troll. Either way is fine.

>>7449722
Please direct me to the post that gave the answer.

>>7449709
This is people when they don't know the answer for sure, but their ego is too big to admit it. Take notes.
It's pathetic.

Fusion is like if you dropped one planet onto another, or let two magnets slam together. The energy comes from the attractive forces between the nucleons.

Fission is like if you cut a string holding two coiled springs against each other (or rather, if you added one more little spring so the string breaks on its own). The energy comes from the repulsive forces between the nucleons.

It's a complicated thing. The forces between protons, which both have a positive charge, are generally repulsive. If you force two protons together, they will only stick very briefly, it is an extremely unstable arrangement. The forces between neutrons are strictly repulsive. Two neutrons will simply not stick together even momentarily.

Pushing protons alone or neutrons alone together would store up energy, and when you let them go, that energy would be released.

So there are only certain combinations of protons and neutrons which are stable. One proton and one neutron will stay together, or two protons and one neutron, or two protons and two neutrons (helium-4, VERY stable), but not one proton and three neutrons or one neutron and three protons. It's a matter of the balance of attractive and repulsive forces.

Further complicating the matter is the weak force, which allows protons to turn into neutrons, and vice versa. Sometimes when you jam two protons together, one will spontaneously turn into a neutron, and then you have a proton and a neutron stuck together. This is the most basic fusion reaction in stars, but the reaction rate is far too low for this to be useful for power generation on Earth.

Fission fuel has pent up repulsive energy, fusion fuel has pent up attractive energy. Either can be exploited for power.

>>7449759
You really can't understand fission and fusion without also understanding neutron absorption and nuclear decay.

A lone neutron is not stable. Most will split into a proton and an electron (with release of a neutrino and energy) in under an hour, many in the first few minutes. It's also rather difficult to get neutrons, due to the nuclear binding energies being so much stronger than the chemical energies we usually deal with at an atomic scale.

However, once you have neutrons, it's easy to have them react with things. Neutrons have only a weak magnetic field, and no static electric charge, so they aren't repelled from nuclei at distance, as protons would be. Ignoring static electric forces, they mostly fly in straight lines until they bonk into a nucleus, and react however they're going to react.

They may bounce off or be absorbed. If they bounce hard enough, they can knock the nucleus apart. If they're absorbed, enough energy may be released to knock the nucleus apart, or it may release energy some other way. A lone proton absorbing a neutron will usually vent its gained energy as a gamma ray and become a stable deuteron, while a complex of two protons and a neutron (helium-3) will settle itself by casting out a proton and becoming unstable tritium, which eventually (with a half-life over ten years) decays back to helium-3.

Decay covers all the ways a nucleus can change without any immediate cause, just from its own internal instability given time. This includes excitation energy being released as highly energetic photons (gamma rays), protons turning into neutrons (by sucking in an electron or spitting out an antielectron) or vice versa (beta decay - a "beta ray" is a fast-moving electron or anti-electron), by spitting out some part of itself (most often a helium-4 nucleus, a bundle of two protons and two neutrons, labeled at first by researchers as an "alpha ray").

>>7449555
>Okay I'm confused. How can you gain energy by going from a low energy state to a high energy state. Wouldn't it be completely opposite? Wouldn't you have to add energy to go to a higher energy state? What am I missing?

"Binding Energy" is how much energy you'd need to pull the system apart, not how much energy is stored up in the system. High binding energy = low-energy state.

>>7449724

>>7449409
>>7449413
>>7449414
>>7449435
>>7449442
>>7449382

And of course,

>>7449371

>>7449672
>If two nuclei need energy to fuse and hold together then were does the gain in energy come from and why?

Atoms have both attractive (the Strong Force) and repulsive (electrical charge repelling protons and protons) forces involved in them.

The Strong Force is very strong, but is very short-range, so it rapidly becomes less effective as atoms get larger.

In small atoms, fusion is like letting two magnets snap together - let them go and they'll do it on their own. However, you have to get them very close to do this, because the Strong Force is short-range, and so to get them close enough to fuse you have to push against their electrical repulsion. This is why fusion reactions take a lot of energy; pushing past this electrical repulsion is difficult. But because the Strong Force is very strong indeed, for small atoms the fusion then releases even more energy.

Once you get to atoms heavier than iron, the strong force has gotten weak enough compared to the repulsion of all those protons that fusion ceases to be profitable; this is why iron is the heaviest element produced in stars.

Fission is just the opposite - the Strong Force is barely holding very heavy atoms together against the repulsion of all those protons, so if you can manage to separate it into smaller chunks against the short-range pull of the Strong Force, the resulting repulsion releases more energy than it took to do that.

>>7450065
The strong force is also repulsive between neutrons.

>>7450084
I mean, it's not just the repulsive electric force acting against the attractive strong force. The strong force adds its own repulsive component to the internal tension that drives fission reactions and alpha decays.

>>7449330

Two particles have 10 energy each

They fuse, new particle has 15 energy.

that excess 5 energy is released

???

Nuclear power

>>7449712
yeah. for some reason i have this thing where i cant bring myself to disappoint choi. like hes my grandpa or something, i just dont want to disappoint him or let him think im stupid. hes a great professor tho so id definitely recommend any of the courses he offers

>>7450087
I did not know that. Thanks! I thought that it was just the weakening of the strong force relative to electrical force that made large atoms unstable.

>>7450369
I'm looking into this, and I might actually have that wrong. Shit.

At any rate, I'm now confident that I do not understand it properly, and you shouldn't take my word on it.

>>7450369
>>7450454
there are models which include a repulsive force for very small distances, which has nothing to do with the reason why very large nuclei are less stable though.

http://www.generalfusion.com/blog/wp-content/uploads/2014/07/General-Fusion-CNS-2012.pdf

>>7449563
Good answer. This means in my opinion that the word fusion is a bit misleading.