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Thread: charge radius of the proton

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    charge radius of the proton

    The proton has a charge radius. Lets say there is a tiny negative charges inside this proton charge radius. What would be the path of a ting negative charge placed in this proton charge radius?
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    The most plausible "tiny negative charge" is an electron. And, as quantum particles, they do not have paths in the classical sense. The electron exists in an orbital, which describes the probability of it's location around, and inside, the proton.

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    Quote Originally Posted by Strange View Post
    The most plausible "tiny negative charge" is an electron. And, as quantum particles, they do not have paths in the classical sense. The electron exists in an orbital, which describes the probability of it's location around, and inside, the proton.
    Thanks Strange, I should have come up with a better way to explain what I was asking. If I had a, large, negatively charged, spherical shell, and Lets say a positively charged argon atom, inside the sphere, what kind of path would it take to the shell?
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    Quote Originally Posted by Copernicus View Post
    Thanks Strange, I should have come up with a better way to explain what I was asking. If I had a, large, negatively charged, spherical shell, and Lets say a positively charged argon atom, inside the sphere, what kind of path would it take to the shell?
    Newton’s shell theorem: there would be no net force on the charged atom (ion).

    As a corollary, I think the electric field inside the sphere is zero (but I may be wrong, it may just be uniform)
    Last edited by Strange; 2019-Nov-25 at 02:31 PM.

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    Quote Originally Posted by Strange View Post
    Newton’s shell theorem: there would be no net force on the charged atom (ion).

    As a corollary, I thought the electric field inside the sphere is zero (but I may be wrong, it may just be uniform)
    you are correct, no field inside a charged sphere
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    Thanks. What about for a non conducting sphere? The edge of the sphere would be positively charged the particles inside would be moving negative charges, so perhaps a gold particle with an extra electron. The non conducting sphere is very large.
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    Quote Originally Posted by Copernicus View Post
    Thanks. What about for a non conducting sphere? The edge of the sphere would be positively charged the particles inside would be moving negative charges, so perhaps a gold particle with an extra electron. The non conducting sphere is very large.
    no
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    I am wondering what would happen if I have the following situation. I have a sphere where the outside is conducting and has a uniform negative charge. The inside of the sphere is non conducting and has a uniform distribution of positive charge. Would there be any movement of the positive charges or negative charges? The total magnitude of the positive and negative charges are equal.
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    no, just read a book about electrostatics and the shell theorem
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    Quote Originally Posted by tusenfem View Post
    no, just read a book about electrostatics and the shell theorem
    I have been reading.
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    Quote Originally Posted by Copernicus View Post
    I am wondering what would happen if I have the following situation. I have a sphere where the outside is conducting and has a uniform negative charge. The inside of the sphere is non conducting and has a uniform distribution of positive charge. Would there be any movement of the positive charges or negative charges? The total magnitude of the positive and negative charges are equal.
    Making the inside non-conducting will have no effect on the electric field for two reasons: (a) a non-conducting material does not, in general, have any effect on an electric field and (b) there is no field inside the sphere.

    You could try asking the question in a different way but the answer will be the same.

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    Quote Originally Posted by Strange View Post
    Making the inside non-conducting will have no effect on the electric field for two reasons: (a) a non-conducting material does not, in general, have any effect on an electric field and (b) there is no field inside the sphere.

    You could try asking the question in a different way but the answer will be the same.
    Everything I read says that there is a field in a non conducting sphere and it is zero at the center and maximum at the edge.

    This is a you tube video. https://www.youtube.com/watch?v=cQy8dborOs4
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    Nah. The field depends only on the charge distribution. Uniform spherical charge distribution - no internal field.

    Grant Hutchison

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    Quote Originally Posted by Copernicus View Post
    Gad, how do people have the patience to sit through these damn things?
    The derivation there is of the field inside a solid sphere. Round about 3:16 he actually tells you that the field of the outer shell "negates itself", and then derives the field created by the central part of the sphere.

    Grant Hutchison

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    Quote Originally Posted by grant hutchison View Post
    Nah. The field depends only on the charge distribution. Uniform spherical charge distribution - no internal field.

    Grant Hutchison
    Did you look at the derivation?
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    See above. Ten minutes of my life you owe me.

    Grant Hutchison

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    So if there is a field inside this insulating solid sphere, how would the charges move inside the solid sphere if the outside of the sphere was conducting and negative. I imagine this is might be a capacitor of sorts? I have not seen a place where this scenario is addressed.
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    Quote Originally Posted by grant hutchison View Post
    See above. Ten minutes of my life you owe me.

    Grant Hutchison
    Ha!
    The moment an instant lasted forever, we were destined for the leading edge of eternity.

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    Quote Originally Posted by Copernicus View Post
    So if there is a field inside this insulating solid sphere, how would the charges move inside the solid sphere if the outside of the sphere was conducting and negative. I imagine this is might be a capacitor of sorts? I have not seen a place where this scenario is addressed.
    As people keep pointing out, a uniformly charged shell will have no effect on any charged particle inside it. So nothing inside your solid sphere will know anything about the negatively charged exterior. Nor will any particle inside the solid sphere be affected by any part of the sphere that lies farther from the centre than its own location. As the tedious YouTube video pointed out, particles embedded inside the sphere will be affected only by the field generated by that part of the sphere that lies closer to the centre.

    It's the Shell Theorem all the way down.

    Grant Hutchison

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    Quote Originally Posted by grant hutchison View Post
    It's the Shell Theorem all the way down.
    Oh, very good.

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    Quote Originally Posted by Strange View Post
    Oh, very good.
    Thank you. I was quietly pleased with it.

    Grant Hutchison

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    Thanks. I just seems weird that one positive charge and one negative charge, so close, would never attract even though the distance to the center is so very much more. Or that there would not be some alternating current that could not create some conductance through that insulating material.
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    Quote Originally Posted by Copernicus View Post
    Thanks. I just seems weird that one positive charge and one negative charge, so close, would never attract even though the distance to the center is so very much more. Or that there would not be some alternating current that could not create some conductance through that insulating material.
    It also seems weird that there would not be some quantum tunneling affect that would not form neutral particles.
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    Quote Originally Posted by Copernicus View Post
    Thanks. I just seems weird that one positive charge and one negative charge, so close, would never attract even though the distance to the center is so very much more. Or that there would not be some alternating current that could not create some conductance through that insulating material.
    All the other negative charges in the rest of the shell counterbalance the one nearby negative charge.

    Similarly, if you kept the Earth the diameter it is now, but compressed all its matter into a spherical shell a metre thick with a huge spherical void inside, the gravity on the surface would still be 1g, but the gravity inside would be everywhere zero - even if you were floating right at the edge of the void with your hand against that shell of super-compressed matter.

    Grant Hutchison

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    Quote Originally Posted by grant hutchison View Post
    All the other negative charges in the rest of the shell counterbalance the one nearby negative charge.

    Similarly, if you kept the Earth the diameter it is now, but compressed all its matter into a spherical shell a metre thick with a huge spherical void inside, the gravity on the surface would still be 1g, but the gravity inside would be everywhere zero - even if you were floating right at the edge of the void with your hand against that shell of super-compressed matter.

    Grant Hutchison
    Thanks.
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    I remember when I was in school, and our science teacher had a van de Graff generator. I loved how the big ball made sparks when you put your hand near it. I said that the inside must be really electrified, and he said no, it is not electrified at all.
    I was so disappointed.
    SHARKS (crossed out) MONGEESE (sic) WITH FRICKIN' LASER BEAMS ATTACHED TO THEIR HEADS

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    If this is all true, why do we need the strong force if we could have all the positive charge on the outside and the negative charge on the inside?
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    Quote Originally Posted by Copernicus View Post
    Thanks. I just seems weird that one positive charge and one negative charge, so close, would never attract even though the distance to the center is so very much more. Or that there would not be some alternating current that could not create some conductance through that insulating material.
    All the other negative charges in the rest of the shell counterbalance the one nearby negative charge.

    Similarly, if you kept the Earth the diameter it is now, but compressed all its matter into a spherical shell a metre thick with a huge spherical void inside, the gravity on the surface would still be 1g, but the gravity inside would be everywhere zero - even if you were floating right at the edge of the void with your hand against that shell of super-compressed matter.

    Grant Hutchison
    Let me remind everyone that the Shell Theorem is exact only in a thought exercise in which the charge is continuous in distribution. If we have a real world shell on which the charged entities were discrete particles and their separation was large compared to the separation of an interior particle and a shell particle, then there will be departures up close to the shell. These departures become virtually zero as we move away inside.

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    Quote Originally Posted by Copernicus View Post
    If this is all true, why do we need the strong force if we could have all the positive charge on the outside and the negative charge on the inside?
    This is the strong nuclear force
    In particle physics, the strong interaction is the mechanism responsible for the strong nuclear force, and is one of the four known fundamental interactions, with the others being electromagnetism, the weak interaction, and gravitation. At the range of 10−15 m (1 femtometer), the strong force is approximately 137 times as strong as electromagnetism, a million times as strong as the weak interaction, and 1038 (100 undecillion) times as strong as gravitation.[1] The strong nuclear force holds most ordinary matter together because it confines quarks into hadron particles such as the proton and neutron. In addition, the strong force binds these neutrons and protons to create atomic nuclei. Most of the mass of a common proton or neutron is the result of the strong force field energy; the individual quarks provide only about 1% of the mass of a proton.
    We need the strong force to have atomic nuclei and thus atoms! Positive charges repel. Almost as soon as positive protons were found to be in atomic nuclei, a force to stop them blowing apart was needed.

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    Quote Originally Posted by Hornblower View Post
    Let me remind everyone that the Shell Theorem is exact only in a thought exercise in which the charge is continuous in distribution. If we have a real world shell on which the charged entities were discrete particles and their separation was large compared to the separation of an interior particle and a shell particle, then there will be departures up close to the shell. These departures become virtually zero as we move away inside.
    Fair enough.
    That reminder of course puts you firmly in charge of responding to all questions about local departures from the Shell Theorem.

    Grant Hutchison

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