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#1
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Jeff wrote:
You are not 'being dense', you are perfectly correct. Waving a magnet will not generate an EM wave, it won't even induce a current unless there is a conductor to hand. Likewise, waving a battery around, won't generate an EM wave either. Maxwell's equations come as a 'set' to generate an EM wave, you can't start with just one. That was one of the flaws in the Cross Field Antenna theory-or the original one, it varied as it was challenged. It had other flaws, eg the idea that the Poynting vector was some 'extra' physical phenomenon which could be 'synthesised', rather than just a mathematical vector representation of the power in the E and M fields. As I pointed out in a previous post, the differential term is zero in the absence of one of the fields so the equations have no, non-trivial, solutions. As I recall, this is one of the standard things you are taught when you attend a lecture on Maxwell's Equations. Perhaps someone missed a lecture (or more),has lost some crucial pages from his notes,or hasn't got a clue. Like all equations, if you apply them correctly, Maxwell's equations do work. However, if you can't understand them, you will mislead yourself. Thank you, Brian, I was beginning to doubt myself there. Not having had the benefit of a University education like Gareth I tend to take an empirical approach to this sort of thing. Unfortunately this time Brian is not correct and a rotating magnet will indeed produce an EM wave. The point that you have missed Brian is that the differential term is zero for a static magnetic field, but when the magnetic field is rotating analysis of the equations reveal that there must be an E field produced in order to satisfy the full set of equations. Have a look at the link in my previous post. Jeff Even if true, the presence of an E field and an H field alone is NOT the same thing as an electromagnetic field. -- Jim Pennino |
#2
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#4
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"Brian Reay" wrote in message
... The question then is, "is the wire loop necessary to produce RF radiation?" Or something similar, yes. Essentially, the rotating field can cause a current to flow in a conductor, that current will produce another magnetic field. The current is charge movement, therefore you have an electric field. That and the 'new' magnetic field can produce an EM wave. No different to any other coil 'excited' with an AC current- perhaps the method of exciting the coil is a little unconventional ;-) Sometimes I am astounded by the things that you come out with; things that perhaps explains your daily output of bluster and the smokescreen that you attempt to creat with your continual personal abuse? |
#5
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Ian Jackson wrote:
snip If a permanent magnet was oscillated inside a loop of wire, it would produce an oscillating current in the loop. An oscillating current would produce RF radiation (especially if it was tuned with a capacitor to the frequency of the magnet's oscillation). In which case you have a generator producing AC voltage. The question then is, "is the wire loop necessary to produce RF radiation?" The wire loop is necessary to produce an AC voltage. An AC voltage applied to an antenna produces RF radiation. Before tubes were invented, high frequency AC generators were used to generate high frequency AC voltage which was applied to antennas. -- Jim Pennino |
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