At 05:07 AM 9/28/99 , you wrote: >From: Anne Ogborn >>>This bring up an idea I had a while back. Is it theoretically possible >>>to have a spherical magnet that has the north pole on the outside and >>>south on the inside? > > >>Nope - div B = 0 >>... > >What you say is true, BUT, As I noted in my reply to this, what really >happens and what appears to happen are different and in this case (Murphy >must have gone on holiday) what APPEARS to happen is what matters. Y' canna >break the laws of Physics but, just sometimes, seeming to MAY BE good >enough. > >Imagine. > >First place bar magnets facing outwards along the main axes in both >directions with, say, Norths out. >Allow a gap in the middle for the Souths to have some separation from each >other. This takes 6 magnets. >Sniff around the outside of this with a hall cell or whatever. You will find >lots of North indicated with weaker spots in between . As long as you stay >outside the sphere mapped by the ends of the bar magnets you will still see >North poles - just of varying strength >Now insert North pole outward bar magnets in the "holes" at 45 degrees (in >every direction) from the existing magnets. You will need 8 bar magnets for >this making 14 in total. >Now with your sniffer you will see an amazingly smooth North pole anywhere >around the sphere. Nope. div B = 0 still. What you get is a bunch of south piles that appear to be inbetween the north poles. You will have an equal flux of North and South poles on your magnet ball. Think of the magnetic field as a continuous arrow leading from the North to South pole. Where the tail is pointing out, it is a north pole, where it is pointing in, it is a south pole. The lines have to connect, unless you have a magnetic monopole- which are theorized, but have never been discovered. There is a theorem (can't remember the name) that excludes the possibility of pure, static, magnetic levitation. There are exceptions, such as with a spinning magnet top (you've probably seen the toy). When it stops spinning, it falls down. Another exception is above a superconductor- since it is an ideal conductor, a magnetic field cannot exist inside it (the Meissner effect), so a sufficiently small magnet can levitate above it. But don't get too strong a B field- a very strong magnetic field will destroy superconductivity. I have seen apparent levitation done with electromagnets, but there was a somewhat hidden sensor which controlled current to the electromagnet. > >Here's a cross section of sorts ... >Questions: > >- Outside the length of the bar magnets, would you see any South poles? As explained above, yes. >- Can you build this on a wire frame? Sure. >- If you placed this on a slightly concave bed of vertical bar magnets with >their North Poles all facing upwards, what would happen? > (make it a continuous North pole with a slightly concave face if you wish. It would quickly roll off to the side. Your concave bed of magnets don't make a truly concave field. If you were to spin the magnet ball to give it some stability and a bit of restoring force, things might ge different, but it would not be permanent levitation. Once it stopped spinning, it would fall down. > >The answers will to some extent depend on magnet sizes, gap sizes, magnet >strengths etc but, I believe, levitation is possible this way. Theory, by >the way, says that it is not. As I noted recently, I have seen SIMILAR >things done and have been told by someone who is usually reliable that they >have done something equivalent to this. I must try it some day ;-) Please do. But don't be suprised when it does not work. But if it does- keep it secret and patent it. You will be rich. I'm not going to go so far as to say Maxwell's laws are perfect or complete, but they do explain electromagnetism as we know it. Matt Bennett