TSny's latest activity
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TSny replied to the thread I Gauss' law seems to imply instantaneous electric field propagation.If the current suddenly stops, ##\partial_t \mathbf{A}## will no longer be zero everywhere. Immediately after the current stops, there... -
TSny replied to the thread I Derivation of Hamilton's Principle: Questions.At which point of the paper do you believe the author takes ##\delta \int L \;dt = 0## for granted? The paper starts with d'Alembert's...
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TSny replied to the thread I Gauss' law seems to imply instantaneous electric field propagation.You're not missing anything. When I posted #9, I was apparently missing something - my brain :oldsmile: The magnetic field in my...
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Hello fellow Physics enthusiasts, I am an aeronautical engineering graduate (Bachelor's) who is interested in Physics and Mathematics...
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TSny replied to the thread Variable mass system : water sprayed into a moving container.I get the same result. A nice approach is to use momentum conservation in an inertial frame moving with the stream of water. After...
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TSny replied to the thread I Gauss' law seems to imply instantaneous electric field propagation.Yes. That's right. In my example, the electric and magnetic fields at any point are time independent. So, no signal propagation can occur.
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TSny replied to the thread I Gauss' law seems to imply instantaneous electric field propagation.The potential at the field point ##p## at time ##t## is given by the retarded-time expression ##\phi(r, t) = \large...
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TSny reacted to bluepilotg-2_07's post in the thread Please tell me where I am going wrong in this integral with
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Hello, thank you for the response! I should have known better, but wasn't considering even and oddness. I realize now that the first... -
TSny replied to the thread Please tell me where I am going wrong in this integral.In the second line, the first integral has an integrand that is odd in ##y##. You cannot replace ##\int_{-\infty}^{\infty}## by...
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TSny reacted to Kostik's post in the thread A Dirac's integral for the energy-momentum of the gravitational field with Like.
@anuttarasammyak Excellent! This was hugely helpful. I wish Dirac had been a little less cryptic. It's not often that one consults...
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TSny reacted to stovenn's post in the thread B Applying the Gauss (1835) formula for force between 2 parallel DC currents with Like.
Aha! I see now how I slipped up by assuming that ##\mathbf{a} = 0## implies ##\ddot{r} = 0##. I had indeed subsequently gotten the...
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There is. If you practice Einstein's summation convention a little, where repeated indices imply summation:$$A_iB_i:=\sum_{i=x,y,z} A_i...
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TSny replied to the thread B Applying the Gauss (1835) formula for force between 2 parallel DC currents.Equation (6) in the link reads $$\ddot r = \frac{\mathbf{r}\cdot \mathbf{\ddot{r}}}{r} - \frac{(\mathbf{r \cdot \dot{r}})^2}{r^3} +...
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TSny replied to the thread I Maxwell stress tensor.The last term on the right is wrong. This term should represent the divergence of just the part of ##E_{ij}## given by ##-\frac 1 2...
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I apparently passed my 15 year PF anniversary earlier this year, but only noticed just now thanks to this post :biggrin: Anyway, I too...
