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A proton can exchange charge with the neutron via a process called "pion exchange". In this process, the proton with quark content $uud$ sends a positive pion $u\bar{d}$ over to the neutron $udd$. The antidown annihilates one down quark in the neutron and adds an up quark, turning the neutron into $uud$, a proton. But what happened to the proton? ...


49

If I put a red billiard ball and a blue billiard ball in a bag, leave them for a while, and then draw one out, I will find I am holding a red ball or a blue ball. Never a purple ball. At the level of fundamental particles, we know from experimental evidence that electric charge is a discrete quantity and behaves like the colour on the billiard balls, not ...


21

Good question! First, the motion of charge between macroscopic objects is defined by classical physics, specifically classical electrodynamics or classical Maxwell's equations to be specific. Nature likes to reach a state of equal charge, but in the microscopic world, things are very different. And an important point to be made, is that your question assumes ...


8

The charge of the proton does not transfer to the neutron because protons are charged particles. For example, when we put two objects of +10C and +20C together and then take them apart, each of them acquires a charge of +15C. This occurs because 5C's net worth of electrons (which are also charged particles – though with the opposite charge to protons) move ...


7

The 2018 Particle Data Group gives a value of $880.2\pm 1.0$ s for free neutron lifetime, as an average of the seven best measurements. As can be seen, the measurements have non-overlapping confidence intervals. As discussed in (Wietfeldt 2014) the different experimental methods do not agree on the value. Wietfeldt gives the formula of the lifetime as $$\...


7

You are correct that a single proton cannot decay into a neutron, positron, and neutrino: $$p\to n+\beta^+ + \bar{\nu}.$$ Based on mass calculations, that is an endothermic reaction. On the other hand, if you can somehow get two protons to fuse and form helium-2 something interesting happens: $$p + p \to \rm{}^2He.$$ This is a very unstable nucleus due to ...


6

or is the theory we have have no correct and there is no need for further debate. You are a hundred years too late to be able to play with the models of nuclear physics. Physics reasearch at present has progressed to the level that has shown that protons and neutrons, not only are the two versions of the"same" particle called collectively a ...


5

I will restrict my answer to a few types of thermal reactors. A thermal reactor uses a moderator to slow fission neutrons down to the thermal energy range where the fission cross section is large. Water provides both moderation and absorbs neutrons. I only discuss light water , H2O, here, and not heavy water, D2O. (D2O is almost as good a moderator as H2O ...


5

Fluorine is rare because its production comes through multiple branching in the main CNO cycle at 17O. The dominant reaction is a (p, alpha) strong reaction producing 14N. The subsequent slowness of the radiative capture (p, gamma) reaction to 15O is why there is lots of 14N. The alternative branch is also a relatively slow 17O (p, gamma) 18F. But 18F is ...


4

In atomic physics we say that only transitions with $\Delta l = \pm 1$ are allowed. Not really. The electronic transitions between different energy levels in atoms are typically restricted to $\Delta l = \pm 1$, but this is not a universal rule. Instead, there is a whole hierarchy of selection rules: electric dipole ("E1") transitions are ...


4

As far as i know, a proton turns into a neutron by emitting a positron This is forbidden at ordinary temperature.You are correct, proton plus proton cannot fuse at ordinary temperatures, this can happen only in the high energy plasma available in star formations and is complicated with a number of interactions. The energy is provided by the high kinetic ...


4

Roughly speaking, it is because the strong nuclear force which binds quarks together is stronger than the electromagnetic force which would otherwise spread the charge more equally. But also, quarks have charges of $e/3$ or $2e/3$ so you can't get a charge of $e/2$. So then the question becomes why do quarks have these charges, and why is charge quantised in ...


3

For example, when we put two objects of +10C and +20C together and then take them apart, each of them acquires a charge of +15C. This is not always true. It is true only if the objects are conductors. If the objects are not conductors then they will each retain their original charge when separated. Why is it that then neutrons has no charge and why does 1/...


3

The constant $V_0$ term is only an approximation to the strong nuclear potential, all that you need to know is that it is attractive (and thus the potential is negative) and this attraction is restricted to a finite range. The nuclear force is actually repulsive at very close distances and falls off with distance, but those are extra details to the problem ...


3

I think it is down to the production mechanism in the case of 14N vs other N isotopes. Nitrogen-14 is the dominant catalysed by-product of the CNO hydrogen burning cycle, which powers stars with mass $>1.5 M_{\odot}$. There has been plenty of time in the universe for such stars to have completed their lives and returned their nucleosynthetic products to ...


3

One way to answer this question is to look at all of the elemental abundances By Swift - Own work, CC0, Link and information about the elements’ origins, By Cmglee - Own work, CC BY-SA 3.0, Link Tantalum is way out in the tail of the other heaviest elements. It’s rare for the same reason that all of the heavies are rare: they have to be produced from ...


2

Well you could read overviews of reactor physics (search using google) or seeif you can find an online schools like Udemy, Edx, or others (again search for online reactor courses). But to really understand it you'll need to understand the math. Reactor Physics, like all physics involves much math. I just found a course by Edx on the basics of physics ...


2

Temperature is a classical thermodynamics variable. Protons and neutrons belong to the quantum mechanical frame that became necessary to be studied when experiments showed disagreement with classical predictions . The photoelectric effect, black body radiation and the atomic spectra could not be explained or modeled with the classical mechanics and ...


2

To what would $^3$He decay (strongly)? The options are: $$^3{\rm He}\rightarrow D+p$$ $$^3{\rm He}\rightarrow 2p+n$$ neither of which makes sense based on mass. A weak decay to $^3$Li is out of the question (https://en.wikipedia.org/wiki/Isotopes_of_lithium#Lithium-3). The fact that tri-neutrons and tri-protons do not exist, not even as resonances, tells you ...


2

The proton charge and the absence of a neutron charge is static. Charge cannot flow between elementary particles as if these were pieces of metal. Analyzing your statement "each of them acquires a charge of +15C", this would only be the case for two conducting objects of exactly the same capacitance. (I assume you check this by taking them apart ...


2

The ${^{280}}{U}{} $ is far from the line of stability and can decay get closer to the line of stability. Consider the nucleus ${^{280}}{U} $, the alpha decay reaction is given by $${^{280}}{U}\rightarrow {^{226}}{\text{Th}}+\alpha$$ If you go about finding $Q$-value for the reaction then you will find that $$Q=[M({^{280}}{U})-M({^{226}}{\text{Th}})-M({^{4}}{...


1

The mass number of an atom is the total number of protons and neutrons in its nucleus. All atoms of the same element have the same number of protons in their nuclei (this is the atomic number of the element), but they can have different numbers of neutrons. A carbon atom with six protons and six neutrons in its nucleus is a different isotope from a carbon ...


1

You ask: If nuclear force is attractive, then why the nucleons don't collide with each other? I think about this, but do not get any proper answer? If by "the nucleons don't collide" you imply "and merge with each other" I want to add to niels' answer that protons and neutrons are in the range where quantum mechanics is needed and ...


1

This is because the strong force has an extremely short range. For the case of two protons, the electrostatic force of repulsion is enough to prevent them from getting close enough for the strong force to kick in, except at very high collision energies. Even then, the strong force attraction is not quite enough to bind them against their mutual electrostatic ...


1

Lets make the comments into an answer: How does this relate to the image below? Are the black lines representative of gluons? The black line represent quarks, the wiggly ones gluons. So are gluons what mediate pion exchange, which is in turn what binds protons and neutrons with the strong nuclear force? The strong nuclear force is a spill over force from ...


1

This old, but interesting experiment performed back in 1932 at a Cavendish Laboratory, shows that some materials (for example liquid hydrogen) when bombarded with neutrons, gives rise to a gamma radiation, which is propagated at a $120°-180°$ angles with respect to incident neutrons. I.e. backwards scattering happens in this case. Assuming that neutron / ...


1

In an accounting of the energy content of a nucleus, the binding energy is negative. When people talk about a "larger binding energy," they are referring to the magnitude of the binding energy. When a massive system goes from small (negative) binding energy to large (negative) binding energy, the masses of its constituents stay the same, but its ...


1

To make an atom of, say, uranium-235, you have to squeeze the protons and neutrons together with tremendous force to get all of them to stick together (just barely). In so doing, you are storing energy in that nucleus and it is then like a cocked mouse trap, waiting for something to trigger it and release that stored energy. The trigger takes the form of a ...


1

Firstly, it is necessary to mention that nuclei are not the only places where the attractive and repulsive forces are in competition. Molecules and solids are other obvious examples: e.g., in a metal the positively charged ions repel each other, just like the negatively charged electrons do. Yet, the system as a whole is stable, due to the attractive forces ...


1

The U238 (and some other isotopes) can't decay with single beta, but only with double beta, because of energetic reasons. The decay product of single beta would have higher energy than the energy of the original nucleus, but with double beta they can decay into a lower energy state. (Look at the isotope masses of U238, Np238 and Pu238, higher mass means ...


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