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B Nuclear Fusion energy questions

  1. Dec 21, 2017 #1
    Hi guys,
    I have been reading about nuclear fusion and I have some doubts that I did not find the answer.
    I understand that the reactants are in a more energetic state than the products when the energy release occurs, however:
    *What triggers the release of energy?
    *Where does the released energy come from?
    *How is it released from the atom?
    Another question, but related to the theme:
    *What defines the stability of a nucleus or particles?
    Thank you in advance.
     
  2. jcsd
  3. Dec 21, 2017 #2

    russ_watters

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    Welcome to PF!

    I find it a bit hard to believe a simple google search didn't immediately turn up the answers to those questions. Could you please post a link to what you've been reading.
     
    Last edited by a moderator: Dec 21, 2017
  4. Dec 21, 2017 #3

    mathman

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  5. Dec 22, 2017 #4
    It will not be possible because I read from various sources. I researched a lot on the subject and did not find the answer, at most it says "the product weighs less than the reagents,so the fusion releases energy", but never because why it releases or what make release. If you can help would be very grateful
     
  6. Dec 22, 2017 #5

    Bandersnatch

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    You need to supply the component nuclei with enough initial energy so as to allow them to overcome electrostatic repulsion (naked nuclei are positively charged due to all those protons). With enough kinetic energy, a nucleus might get close enough to another, where at certain distance the attractive strength of strong nuclear force is greater than the electrostatic repulsion. At that point the nuclei preferentially bind together in a system of lower energy state, and the difference in energy states is released as energy.
    This is similar to lighting a match - you need to supply some initial energy to get over some potential barrier preventing the components from binding in a more strongly bound configuration (the latter releasing more energy than was needed to overcome the barrier).

    From the potential energy of the components. As they settle into a more tightly bound configuration, the difference between initial and final potential energy is released - same as with a rock falling from height.

    Depends on the specific reaction, but in general it can be released as kinetic energy of the products, radiation, or particles (e.g. neutrinos, electrons, positrons).

    The interaction between repulsive and attractive forces. In the case of nuclei, it's the repulsive electrostatic force from protons and the attractive strong force between protons and neutrons. The two have different ranges and strengths, so there exist combinations of protons+neutrons that make for more stable nuclei than other configurations.
     
  7. Dec 22, 2017 #6

    russ_watters

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    They must have been pretty weak sources. Even the wiki article can answer pretty much all your questions. (someone already posted it)

    Please let us know if there is anything in particular you are still having trouble with.
     
  8. Dec 29, 2017 #7
    Can you tell me more about the potential energy you quoted? Potential energy in nuclear fusion
     
  9. Dec 29, 2017 #8

    Bandersnatch

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    Are you familiar with how potential energy in a gravitational field is converted into other kinds of energy as two gravitating components are brought together?
     
  10. Dec 29, 2017 #9
    Yes. I studied only about gravitational potential energy and the one you mentioned to me seemed strange to me, if possible, I would like you to explain better about that potential energy you are quoting
     
  11. Dec 31, 2017 #10

    Bandersnatch

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    Sorry for the sporadic replies - it's that time of the year.

    So, with an object in a gravitational field, it has some potential energy associated with its separation from the source of the field. As the attractive force brings it closer to the source, the object exchanges its potential energy for other kinds of energy. Normally it's just kinetic energy, but when e.g. an asteroid finally hits the surface of a planet, its kinetic energy is further converted into heat, radiation, or kinetic energy of fragments ejected upon impact. In any case, whatever energy you count as released at some later stages, it must have come from the gravitational potential energy.

    It's similar with fusion reactions. You have some components in an attractive force field, albeit this time it's the strong nuclear force rather than gravity, which have some potential energy associated with their separation. As you bring them closer together the potential energy is exchanged for other kinds of energy. These other kinds may manifest as kinetic energy, radiation (photons), or massive particles (electrons, neutrinos, etc.).
     
  12. Jan 2, 2018 #11
    thanks a lot,guys
     
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