Does a magnetic field rotate with a magnet...the answer!
in [Physics]
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From: Benj on 23 Feb 2010 03:13 From the time of Faraday the question has remained "does a magnetic field rotate with a rotating magnet? Rotate a cylindrical magnet on it's axis and the question is does the field move with the magnet? In other words in qV x B is relative motion between the test charge q and the "postion" of the magnetic field B (whatever that means)? The answer it seems (like so many correct ideas that expose the lax thinking of modern physics) is found in Jefimenko. In this case in his book on causality and electromagnetic induction. The answer is ... it doesn' matter! Jefimenko clearly derives the causality conditions for electric and magnetic fields. Electric and magnetic fields clearly DO NOT create each other. Faraday "magnetic induction" has NOTHING to do with a magnetic field! A changing magnetic field does NOT induce a current or voltage in a conductor! And even worse, the magnetic field related to a moving magnet does NOT create the vxB Lorentz forces. This is strong stuff. Instead what happens is that it is a current and it's variations that creates the E field about itself in space. And further more it is a current moving at constant velocity in the direction of it's flow that not only creates an induced E field but a static "ordinary" one as well. The VALUE of the combination of these two E fields is given by VxB. As far as is known ALL magnetic fields come from currents. A permanent magnet can be seen to be a set of currents flowing around atoms. These circular currents cancel where they touch throughout the body of the magnet. They don't cancel on the outer surface. Hence the equivalence between say a cylindrical magnet and a current-carrying solenoid. Both represent current flow around the outside of the cylinder. Hence in a Faraday generator, if one wants to know the relative motion between parts it relates to the motion between the circular currents of the permanent magnet and the rest of the apparatus. The relative motions that count are between the magnet BODY and the Disk and wires of the rest of the generator. The magnetic field is actually irrelevant and it doesn't matter what it does! Jefimenko does it again!
From: Cwatters on 23 Feb 2010 03:46 "Benj" <bjacoby(a)iwaynet.net> wrote in message news:201803fa-a4f9-437b-9a55-9294a391e8de(a)q29g2000yqn.googlegroups.com... > As far as is known ALL magnetic fields come from currents. A permanent > magnet can be seen to be a set of currents flowing around atoms. These > circular currents cancel where they touch throughout the body of the > magnet. They don't cancel on the outer surface. Perhaps you can explain why the power handling capability of a transformer core depends on it's volume..
From: Benj on 23 Feb 2010 04:35 On Feb 23, 3:46 am, "Cwatters" <colin.wattersNOS...(a)TurnersOakNOSPAM.plus.com> wrote: > "Benj" <bjac...(a)iwaynet.net> wrote in message > > news:201803fa-a4f9-437b-9a55-9294a391e8de(a)q29g2000yqn.googlegroups.com... > > As far as is known ALL magnetic fields come from currents. A permanent > > > magnet can be seen to be a set of currents flowing around atoms. These > > circular currents cancel where they touch throughout the body of the > > magnet. They don't cancel on the outer surface. > > Perhaps you can explain why the power handling capability of a transformer > core depends on it's volume.. That would be because saturation of magnetic materials is a material property. Any more questions?
From: nuny on 23 Feb 2010 04:58 On Feb 23, 1:35 am, Benj <bjac...(a)iwaynet.net> wrote: > On Feb 23, 3:46 am, "Cwatters" > > <colin.wattersNOS...(a)TurnersOakNOSPAM.plus.com> wrote: > > "Benj" <bjac...(a)iwaynet.net> wrote in message > > >news:201803fa-a4f9-437b-9a55-9294a391e8de(a)q29g2000yqn.googlegroups.com.... > > > As far as is known ALL magnetic fields come from currents. A permanent > > > magnet can be seen to be a set of currents flowing around atoms. These > > > circular currents cancel where they touch throughout the body of the > > > magnet. They don't cancel on the outer surface. > > > Perhaps you can explain why the power handling capability of a transformer > > core depends on it's volume.. > > That would be because saturation of magnetic materials is a material > property. > Any more questions? Permanent magnets are made of "magnetic materials", and are typically saturated during magnetization. Power transformer cores are also made of "magnetic materials", but are designed NOT to reach saturation during normal operation. What does "a materials property" mean in this context? Mark L. Fergerson
From: bert on 23 Feb 2010 08:28
On Feb 23, 4:35 am, Benj <bjac...(a)iwaynet.net> wrote: > On Feb 23, 3:46 am, "Cwatters" > > <colin.wattersNOS...(a)TurnersOakNOSPAM.plus.com> wrote: > > "Benj" <bjac...(a)iwaynet.net> wrote in message > > >news:201803fa-a4f9-437b-9a55-9294a391e8de(a)q29g2000yqn.googlegroups.com.... > > > As far as is known ALL magnetic fields come from currents. A permanent > > > > magnet can be seen to be a set of currents flowing around atoms. These > > > circular currents cancel where they touch throughout the body of the > > > magnet. They don't cancel on the outer surface. > > > Perhaps you can explain why the power handling capability of a transformer > > core depends on it's volume.. > > That would be because saturation of magnetic materials is a material > property. > Any more questions? Field flows from south pole to north pole,and is in constant motion. This is shown to us by its "lines of force" (compass) Turn mechanically an iron rotor into this field and pickup electrons and you have a generator. Have electrons enter this field and the iron rotor will turn,and you hhave an electric motor.Thus you see how both are the same. Two sides to the same coin. Both just hum,as they receive or transfer energy in the nicest way. Just one moving part. TreBert |