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Apr
13
revised Can I take the partial derivative of the Lagrangian with respect to a constant?
clarified last sentence
Apr
13
answered Can I take the partial derivative of the Lagrangian with respect to a constant?
Apr
12
reviewed Approve How did Feynman prove that energy cannot be extracted from electric field?
Apr
12
reviewed Reject Why do we fall down when the bicycle slows down?
Apr
12
answered Question regarding charge and acceleration
Apr
12
comment How did Planck derive his formula $E=hf$?
Just as a lead: what I heard was that Planck (or maybe someone else) discovered an exact form of the blackbody radiation formula which goes like $\nu^3 (e^{C \nu}-1)^{-1}$. He then spent months working backwards from this formula to try to find what physical assumptions he needed to get it, and he found quantization of energy levels in an oscillator $E=n \nu h$ did the trick. (C depends on $h$, $T$ and $k_b$). This is consistent with what is on en.wikipedia.org/wiki/Planck_postulate
Apr
12
comment How does the magnetic field generated from a rectangular cross-sectional current-carrying conductor differ from a circular cross-sectional conductor?
@AdamM-W Oh, you want to know how to numerically calculate it? That might belong to a separate question. High precision would probably be totally useless for you, for engineering/practical calculations, because only the highest order term $\mu_0 I/(2 \pi r)$ will be significant. At most, you'd go to a second order term (in a "multipole expansion"). Anyways, the formula in the paper you linked is just the integral of the vector potential of a wire (the infinitesimal wire can be taken as an infinitesimal "current element").
Apr
11
answered Time relativity / paradox
Apr
10
reviewed Approve Could the LHC be used for fusion experiments?
Apr
8
reviewed Edit What is Timelike Quantum Entanglement?
Apr
8
revised What is Timelike Quantum Entanglement?
title correction
Apr
6
reviewed Reject and Edit How can the contact point of rolling body have zero velocity?
Apr
6
revised How can the contact point of rolling body have zero velocity?
edited tags, improved previous edit suggestion
Apr
6
reviewed Reject Calculating charge density
Apr
6
comment Would a spinning, evenly charged sphere generate a magnetic field?
@HolgerFiedler the magnetic field of a charged spinning spherical shell is exactly like a point dipole outside the surface: hep.princeton.edu/~mcdonald/examples/rotatingshell.pdf and is not "along the z axis", and Marcel's answer does not state that. The equations you are using are confused and are used without meaning. The equation $\nabla \times B=\mu_0 J$ contains different physics than the Lorentz force law.
Apr
6
comment Would a spinning, evenly charged sphere generate a magnetic field?
@HolgerFiedler it DOES mean rigid body, but all the FORCES involved are supplied by the structural integrity of the field. Your equation has nothing to do with the field actually generated by the charges. The Lorentz force law does not give you the field generated by the charges.
Apr
6
revised Lagrangian formalism (demonstration)
added 30 characters in body
Apr
6
answered Lagrangian formalism (demonstration)
Apr
6
comment Would a spinning, evenly charged sphere generate a magnetic field?
@HolgerFiedler your formula would give the needed $\vec{B}$ field to support the charges moving in circles, as if the charged sphere itself had no structural integrity. Which is not relevant to the question that was asked. (That's why people are saying you're wrong -- "F" is irrelevant to the question asked so there's no reason why "$F\cdot qv$" should mean anything, let alone be zero).
Apr
5
answered How does the magnetic field generated from a rectangular cross-sectional current-carrying conductor differ from a circular cross-sectional conductor?