Talk:Charge density

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Like in nuclar phhysics - for low concentrations of ionizing mass the functions of ionization of atoms (i.e. elements being built up - hydrogen to helium Fusion; or lower grade elements; Fission) It was noted for years that ionization was simply proportional to the mass untill it was realised that a slow compound effect occured thus compounding this to a Cytical mass wherw it all converted in a split second. The logical questioned asked; what has this to do with Charge (Coulomb) density i.e. C/m, C/m^2 or C/m^3. Another question I'll ask to further clarify where are we going with this is. What is the maximum temperature? Stephen Hawkins stipulated that at the conception of the universe that its temperature was infinnity (yeh yeh); Any logical person could shoot that idea down. The thing is if you dont realy know units in terms of m mass, L Length & time. you are going to have a hard time understanding extrapulation ideas into new physics. I'll give you an example, I prior asked whats the maximum temperature & if it exist we know the lowest 0 deg K (-273.15degC) now Stephen says it is infinity - I'll show how simply he is WRONG by ussing SIMPLE logic. At absolute temperature 0 degrees C nothing moves i.e. all mass electons freze that is all particles are at Zero velocity and as the mass is heated the particles increase their oscilation / giration / vibrating / speeding such as gasses - it is logical to conclude that the particles can't go past the speed of light 3p8 m/s (3x10^8 m/s) Thus Mr Hawkins you have a flaw in your theory & the units for all temerature scales (C, F, R (Rankin) K ( Kevin)) dont show their units at all & are trully Length/Time ie say m/s (metre/second). Which brings me to another question I believe their is only one maximum that is readily reconised in physics that being the velocity of light being c (3p8 m/s. I'snt that good I,ve found another maximum (temperature) or have I as it is another form of the speed of light as temp is velocity. Just a few other units that are not qualified by proper units in terms of mass energy length time (melt) are Amp Volt Coulomb etc etc this in itself makes it hard to fully comprehend what it is. I have computed most of these gray units & have found many maximums right up to why the universe is expanding at an increace rate. Kevin SAYERS Werribe 3030 Australia. kev.7@bigpond.com —Preceding unsigned comment added by 124.191.103.42 (talk) 11:04, 1 March 2010 (UTC)

Relation to DFT

Seeing how DFT relies on the charge density, perhaps the relation between the two should be mentioned? — Preceding unsigned comment added by Adacadin (talk • contribs) 17:41, 9 April 2011 (UTC)

Assessment comment

The comment(s) below were originally left at Talk:Charge density/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

Charge density is also important in relation to chemistry. Chanrge density- the charge per unit volume of an element increases from left to right on the periodic table of the elements, and also increases from bottom to top on the periodic table of the elements. for example; The Li+ ion is smaller than the K+ ion, so the charge density of the Li+ ion is greater than that of the K+ ion. Ions with greater charge densities can attract polar molecules (like water) more easily.

Last edited at 21:15, 28 November 2006 (UTC). Substituted at 11:16, 29 April 2016 (UTC)

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Orphaned references in Charge density

I check pages listed in Category:Pages with incorrect ref formatting to try to fix reference errors. One of the things I do is look for content for orphaned references in wikilinked articles. I have found content for some of Charge density's orphans, the problem is that I found more than one version. I can't determine which (if any) is correct for this article, so I am asking for a sentient editor to look it over and copy the correct ref content into this article.

Reference named "Purcell":

• From Electric field: Purcell, Edward (2011). Electricity and Magnetism, 2nd Ed. Cambridge University Press. pp. 8–9, 15–16. ISBN 1139503553.
• From Inductance: Purcell, Edward M.; David J. Morin (2013). Electricity and Magnetism. Cambridge Univ. Press. p. 364. ISBN 1107014026.
• From Electrostatics: Purcell, Edward M. (2013). Electricity and Magnetism. Cambridge University Press. pp. 16–18. ISBN 1107014026.
• From Capacitor: Purcell, Edward (2011). Electricity and Magnetism, 2nd Ed. Cambridge University Press. pp. 110–111. ISBN 1139503553.
• From Electrostatic induction: Purcell, Edward M.; David J. Morin (2013). Electricity and Magnetism. Cambridge Univ. Press. pp. 127–128. ISBN 1107014026.

I apologize if any of the above are effectively identical; I am just a simple computer program, so I can't determine whether minor differences are significant or not. AnomieBOT⚡ 22:44, 14 December 2017 (UTC)

Charge density in quantum mechanics

The introduction states: `the charge of an individual particle is not concentrated at a point but is 'smeared out' in space and acts like a true continuous charge distribution.[4]'

The section `Charge density in quantum mechanics' states `In quantum mechanics, charge density ρq is related to wavefunction ψ(r) by the equation

{\displaystyle \rho _{q}(\mathbf {r} )=q|\psi (\mathbf {r} )|^{2}}{\displaystyle \rho _{q}(\mathbf {r} )=q|\psi (\mathbf {r} )|^{2}}'.

I'm not an expert on this topic, but the situation seems more complicated than the above statements suggest. Feynman, for example, states`The wave function ψ(r) for an electron in an atom does not, then, describe a smeared-out electron with a smooth charge density.' and there seems ongoing research in this area (for example).

If there is an expert out there who could clarify the situation, that might be helpful.

D.Wardle (talk) 22:00, 21 February 2020 (UTC)

References

The equation in the quantum mechanics section you quote is the Born equation: $\rho _{q}(\mathbf {r} )=q|\psi (\mathbf {r} )|^{2}$ which expresses the spread-out nature of the charge. It says the charge density in space of a quantum particle is proportional to the squared magnitude of the wavefunction. Since the wavefunction is a continuous function throughout space, the particle's charge acts as if it is also.

The Gao article you mention simply confirms the Schrodinger-Born view: "This article re-examines Schrodinger’s charge density hypothesis, according to which the charge of an electron is distributed in the whole space... It is demonstrated that... the results as predicted by quantum mechanics confirm Schrodinger’s original hypothesis."

The Feynman quote you give is his explanation of the well-known principle of wave-particle duality. The electron interacts with matter as a particle. From the Born equation, the wavefunction gives the probability of the electron being located at different points. But as long as the position of the particle is not localized, due to the uncertainty principle its charge acts as though it is spread out in space, as a continuous charge density.

The view of electron orbitals as continuous clouds of charge density is the foundation of atomic physics and chemistry. I'll add some citations. --Chetvorno^TALK 13:04, 8 March 2022 (UTC)