Aug 7th 2017, 01:58 PM
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Member
Join Date: Jul 2015
Posts: 84
| A basic question about magnetism
I would like to ask a seemingly daft question. What is the experimental evidence for the traditional magnetic flux, as described by people such as Faraday, Maxwell and Fleming?
We need to bear in mind that this magnetic flux was based on an ignorance of magnetism - orbiting and spinning electrons were unknown 150 years ago. I have asked in vain for evidence of this flux. It seems to be just a guess which turned into a belief.
Suppose magnets had been unknown at the time. Experiments with electricity would then have led to a simple law: like currents attract and opposite currents repel. This basic law then explains magnetism, such as the alignment of iron filings around a magnet. Imagine for example that two bar magnets have stuck themselves together side by side, i.e. with north poles touching south poles. The circulating charges in the two magnets are, at their closest, moving in the same direction - a bit like cog wheels meshing together. Hence there is a net force of attraction.
Using Ockham’s principle, the complication of a circular perpendicular field is then unjustified. (Instead of Biot and Savart’s law to predict flux density, the attraction between elements of two current vectors is dF = k I1.I2 ds1 ds2 /r^2 where k depends on the permeability.) So magnetic forces just act along the straight lines between moving charges. This is the same simple principle that works for electrostatic forces between stationary charges. We need not assume the universe uses two completely different force mechanisms. Motion just modifies the electric field.
Traditional magnetic fields are defined as continuous. So the field emanating from the north end of a bar magnet loops round the outside of the magnet to the south pole and returns through the magnet’s body back to the north pole. Now imagine a magnet made of a very viscous material that allows a free-moving north pole to drift within it. This internal north pole would be repelled by the magnet’s south pole (?) and leave again through its north pole. We are all taught this stuff, but it doesn’t make sense to me. We should not view magnets as perpetual motion machines. Forces begin and end at points: they do not keep going round in circles. There is a measurable energy gradient along a real force field, but there can be no such gradient around a continuous loop.
Magnetic flux represents the total "lines of force" through a surface, but no force can be detected along these lines. The notion of circular fields perhaps arose when rings of iron filings were seen around a conducting wire, but it was a very odd idea. The circular magnetic field at any point is defined as a vector that is perpendicular to the force it produces. However, if a vector represents something that measurably exists, e.g. a physical force, a wind velocity, a flow of energy or a stampede of hamsters, its perpendicular components are zero. So we can say that a magnetic field having its greatest effect in a perpendicular direction does not exist.
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