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Is 1 mm/s realistic for you?
It uses conventional current, as if we didn't know about electron yet.
Quote from: hamdani yusuf on 09/01/2025 02:03:00Is 1 mm/s realistic for you?See reply #451 above.Quote from: hamdani yusuf on 09/01/2025 02:16:50It uses conventional current, as if we didn't know about electron yet.All classical electrodynamics uses conventional current. Some conductors use hole mobility, so the classic sign convention just gives us consistent models. And in my book 0.1 mm/s is a good as stationary compared with c.
The article I quoted disagrees.
Quote from: hamdani yusuf on 09/01/2025 12:01:30The article I quoted disagrees.Then it was clearly written by someone who knows nothing of electrodynamics, or is unable to evaluate his own equations
https://physics.weber.edu/schroeder/Daniel V. SchroederDepartment of Physics and AstronomyWeber State University1415 Edvalson Street, Dept. 2508Ogden, UT 84408-2508USAOffice: Tracy Hall Science Center 322Phone: (801) 626-6048 (messages are checked infrequently)email: dschroeder@Weber.eduBiographyI was born in St. Louis, Missouri, and grew up in the suburb of Webster Groves. From 1980-84 I attended Carleton College, and from 1984-90 I was a graduate student at Stanford University, where I spent most of my time at the Stanford Linear Accelerator Center. I taught physics at Pomona College for one year and at Grinnell College for two years before coming to Weber State in 1993.
The most obvious mistake is using v to denote two different speeds.
Next, is a failure to provide a numerical value for his derived magnetic force and compare it with experiment.
This can be simply solved by adding indices or subscripted letters.
Quote from: hamdani yusuf on 11/01/2025 11:53:23This can be simply solved by adding indices or subscripted letters.Which he didn't do.
The results in the last experiment has a pattern.The first graph shows the voltage measurement against the weight/charge ratio of the salts.The second graph shows the voltage measurement against the weight/charge ratio of the salts, when the charge of MgCl2 is "corrected" to make the graph linear.The second graph shows the voltage measurement against the weight/charge ratio of the salts, when the molecular weight of MgCl2 is "corrected" to make the graph linear.
I was always wondering whether the electromagnetic fields are real or just mathematical objects. This is how I understand it now after some years of studying physics.
I believe that magnetic "Lines of Force" are a nonsensical construction that emerged because the iron filings used to explore magnetic fields arranged themselves into lines. The field is clearly continuous, and any lines made visible from iron filings are an emergent property of iron filings sprinkled onto the paper over a bar magnet. All this should be obvious, but one still runs across people that speak of "lines" as if they were a fundamental part of nature.
Electro-Maganetic fields are as real as gravity! Math is just a language to describe reality. They are both testable and so are scientific realities.
Magnetic field lines are no more real than contour lines on a map or isobars on a weather chart. Magnetic field lines are drawn in line with the field gradient, whereas the others I mentioned are perpendicular to their gradients.
Excellent presentation. Thanks. It seems to me that there's another conundrum. I read some where that the vector cross product does not exist in any randomly chosen number of dimensions. It does exist in 3 dimensions and in 7 dimensions. This means that you can't imagine that there are 4 dimensions of space because maxwell's equations would not work. But you can imagine that there are 7. The conundrum will be, however, if the 7 dimensional meaning of cross product is the same as the 3+1d version if we are trapped in a 3+1d brane in 7+1d space. But it's it the same? If not, that could eliminate the possibility that we live in universe with a higher number of dimensions - wouldn't it?
This equipment shows the electromagnetic force acting on two parallel current carrying wires. When the currents are in the same direction, there is an attraction force between the two wires. When the currents are in the opposite direction, there is a repulsion force between the two wires. The force is caused by the interaction of the circular magnetic field produced by each wire.
If the conductor is shielded with a conducting foil eg. Aluminum, your theory does not work because electric charges do not interact thru the shield. But the constant magnetic field passes thru the non magnetic shield as every pupil knows. How comes that?
A solid metal ring is placed on an iron core whose base is wrapped in wire. When DC current is passed through the wire, a magnetic field is formed in the iron core. This sudden magnetic field induces a current in the metal ring, which in turn creates another magnetic field that opposes the original field. This causes the ring to briefly jump upwards.If there is a cut in the ring, it cannot form current inside it, and thus will not jump.When the ring is cooled in liquid nitrogen, the resistance of the metal is lowered, allowing more current to flow. This lets the ring jump higher. However, the magnetic field curves away at the top of the iron coil, meaning with DC power, the ring will never fly off the top.When AC current is passed through the wire, the ring flies off the top of the iron core. This is due to the fact that the current lags the emf by 90 degrees in inductors (which is what we have here). This yields forces on the ring that are always pointing upwards, even as the current oscillates.
No, the current inducted in the ring is always the opposite direction of the current in the coil, so the magnetic field of the ring always opposes the iron core's, and always is repelled. Think of the AC current demo, the current's direction is switching 60 times a second, but the ring only moves away from the coil.
well its not exactly accurate although close. When dc is connected you have an initial changing magnetic field- as the dc current rapidly changes from zero to full current flow, this change in magnetic field induces current in the ring and it jumps. But the dc current reaches a peak and is then steady non changing current, therefor can no longer induce current in the ring. In the ac current, the magnetic field is constantly changing, therefor current constantly induced in the ring, so keeps goin
Physics Ninja calculates the magnetic field produced by a spinning disk of charge Q. The charge is uniformly spread on the surface of the disk and the disk spins at a constant angular frequency omega. The exact results is found and the limit of the result is evaluated for a point far from the disk.
Had a real experiment ever been done to demonstrate and calculate the magnetic field of a rotating charged disk? Or only thought experiments?Asked 1 year, 9 months agoModified 1 year, 9 months agoViewed 125 timesI have been trying to find if a real experiment has ever been done to prove and calculate the magnetic field of a rotating charged disk, whether it's a conducting or a non-conducting charged disk. All I found on Google and YouTube are just thought experiments, so please if anyone had come across an actual experiment let me know.https://physics.stackexchange.com/questions/768930/had-a-real-experiment-ever-been-done-to-demonstrate-and-calculate-the-magnetic-f
From Wikipedia: Arago's rotations is an observable magnetic phenomenon that involves the interactions between a magnetized needle and a moving metal disk. The effect was discovered by Fran?ois Arago in 1824. At the time of their discovery, Arago's rotations were surprising effects that were difficult to explain. In 1831, Michael Faraday introduced the theory of electromagnetic induction, which explained how the effects happen in detail.
5K20.42 Magnetic Induction Disk (Arago's Rotations)A pulley wheel turns a copper disc under a plastic box which rotates a magnet above.
In 1825, the French astronomer and physicist Dominique Fran?ois Jean Arago (1786-1853) observed that if a horizontal magnetic needle is suspended above a copper disc and the disc is rotated around the vertical axis, the needle starts to rotate in the same direction. In order to carry out this classical experiment, a number of constructions have been conceived and built over the past almost 200 years. Now I was able to get hold of such a historical device. I estimate that it was built between 1850 and 1880 and is made of solid walnut and brass. In addition to the two copper discs, there was certainly a third one, one with radial slots. Also the glass disc and the magnetic needle were missing and were copied.With the help of a crank, a conical friction gear is driven which brings the rotation into a vertical axis and simultaneously increases the speed. The friction wheel on the crank side is made of walnut wood and the friction surface is covered with chamois leather. Several, thick leather disks, which are tapered, form the second friction wheel which drives a turntable via a vertical shaft. This can be covered with one of the two existing copper discs. Above this turntable and thus above the copper disc a round glass disc is fixed in a brass ring which has the purpose to demonstrate that no air friction or similar causes the magnetic needle to rotate. Furthermore, the glass plate carries a small tripod on which the magnetic needle rests rotatably.The physical effect is no longer spectacular from today's point of view, but at the time of its discovery it certainly caused smoking heads, because a non-magnetic material was able to send force effects through a glass pane. The fact that these are eddy currents in copper, i.e. induction, was only discovered a few years later. The proof was achieved by using radial or circular concentric slits instead of a solid copper disc. The eddy currents are prevented from spreading through these slits; thus the associated magnetic field can no longer attain the strength of a solid disc. Consequently, the magnetic needle remains almost at rest.
//www.youtube.com/watch?v=x8gnQhM3fJYQuotePhysics Ninja calculates the magnetic field produced by a spinning disk of charge Q. The charge is uniformly spread on the surface of the disk and the disk spins at a constant angular frequency omega. The exact results is found and the limit of the result is evaluated for a point far from the disk.Has anyone done the experiment?