A curious experiment can you solve it?

[jammieg]

Here's a curious experiment see if you can guess what will happen and more importantly figure out why it does what it does, to date no one seems to have given a clear answer, no one seems to know how this works including myself.

 

take a bar magnet and tie a string in the middle, then suspend it and twist up the string or rubber band whichever you like so that when released the magnet will spin such that the poles are rotating parrellel to the horizon( you can put a small electric motor to the end of the string also which is what I did eventually it works better). Now that your magnet is spinning take another magnet in hand and hold either pole next to the spinning magnet, here's where you guess what will happen, given the north end of the pole is going to rotate around to the stationary magnet pole just as often as the south end common sense would say it should not move- nothing should happen maybe some vibrations, but does the spinning magnet repel from the stationary one, stay where it is, or attract to it? I'll answer below so don't look down yet.

 

 

 

 

 

 

Oddly the spinning magnet always attracts to the stationary one, why it does this I don't know and I wonder if someone would care to attempt to explain why...after 2 years I haven't found anyone who could or maybe they just don't care to explain it or i'm not explaining it right.

[Sisyphus]

That is odd. What happens when you vary the speed of rotation and the distance between the two magnets? Answering that might help, but that's just a guess.

 

Some other guesses:

 

Irregardless of spinning, the south pole is still attracted to the stationary magnet, and the north pole repulsed. Thus, a uniform force acting to rotate the magnet will still result in a greater net force of rotation as it is moving towards its preferred allignment, and less when it is moving away. Thus it spends slightly more time with south to north than with north to north, and the net result is attraction.

 

Also, if it is spinning fast enough, and is far enough away, then the two poles would effectively cancel out, making it equivalent to an umagnetized bar of iron, which would be attracted in any case. So the attraction is greater than the repulsion, anyway.

 

[/uninformed speculation]

[Waldo]

Ya this is complete shot in the dark but did you try spinning the magnet the opposite direction, perhapse that would repel the other magnet.

 

to me, having not much magnet information, i would believe that the spin is changing the direction of the normal megnetic force? Thats just a guess very interesting though.

[Klaynos]

These are idle speculations....

 

I would guess that the oscillation is slowing down so that it is spending more time...

 

N S

S N

 

Also with the motor you must remember that the magnets inside could be oscillating seperate to the whole thing so sould be spending all their time aligned.... Hence the greater effect...

[jammieg]

I think Sisyphus and Klanos are on to something, I've been puzzling over for a few years now in spare time, I think this is the start, but please elaborate slow it down for us, break it down and explain it like we are all 8 years old, why would the north end of the magnet spend more time aligned with the south pole of the stationary one than the south end with the same south pole of the stationary one? What exaclty is going in there?

 

Also as the speed increaes the force of the attraction deminishes, and like we would have thought as the distance increases that same force demenishes I haven't plugged in the numbers yet I wan't really interested in those. I did try opposite spinning directions with the same results, there are some other curiousities of this experiment but this is the main one, also wether an electic motor is used or simply the stored up twisted energy of the string itself the results are the same.

I do kinda remember that magnetism's force tappers off to the distance in cube roots instead of squars like gravity for instance so it's much weaker over great distances like gravity but still wether it's 1 millimeter or 1 trillion miles it would still exert a very small amount of attraction to the stationary one i guess.

[DV8 2XL]

What I think is happening is hat the attraction that the spinning magnet will feel when the poles are aligned PLUS the attraction that it will feel when the poles are at right angles to each other adds up to a net attraction.

[YT2095]

I ran a "Thought experiment" I think this MAY help answer it for you.

the problem lies in the actual Bar Magnet.

there is only a Small portion of it that will actualy Repel, the rest is either Passively atracted or positively atracted.

the middle section will be pulled buy either north or south, only the very end and close to it will be repeled.

so you have 25% repel 50% passively atracted, and 25% Positively atracted.

the odds are in favor of atraction

 

the middle bit may as well be an iron nail, and nails never repel.

 

 

that`s My Hypothesis on the matter anyway

[woelen]

I think that indeed it all boils down to the fact that the magnets are made of metal and the experimental outcome is not that surprising to me.

 

There are two types of forces. We have the true magnetic force, due to the fact that both pieces are magnets, but we also have a second component, being the plain attraction of iron (or some other ferromagnetic material) to the magnets.

 

The true magnetic force is perfectly alternating and has average value 0. The plain attraction of ferromagnetic material always is present and results in a net attraction. So, the total average force will be attracting. This is what the others also mentioned already.

 

---------------------------------------------------------------------

 

The experiment would become really interesting if "ideal" magnets could be used, which only exhibit magnetic fieldlines, but do not add the effect of their material being attracted by the other magnet. Even with such magnets, I can imagine that the experimental outcome still can be very surprising.

 

A somewhat related effect exists for electrostatic forces. Many people think that a charge distribution, which looks as follows:

 

+-................................................................................+-

 

does not feel any attracting forces (with the + and - charge rigidly attached to each other, and ...... representing empty space). Suppose the distance between + en - is small, relative to the length of ......, but still non-zero. Then such a system shows a net attractive force, provided the dipole objects +- are free to rotate. This net force is very small, but it nevertheless exists. It only is present as second order in the distance between the +- charges inside a dipole object. They orient themselves in a fashion as shown above. In chemistry this effect is known as "Van der Waals" force. A similar effect may be present in the experiment with the magnets, where the rotating magnet is allowed to move away from the fixed magnet or move towards it (so, translation is allowed besides rotation). The complicated motion patterns may result in a second (or even higher order) average attracting force.

[Meir Achuz]

"The plain attraction of ferromagnetic material always is present and results in a net attraction."

That is about what is happening. A magnet will attract non-magnetized iron as strongly as if it were magnetized.

A better way of seeing it is to note that the attractive force between two bar magnets is stronger than the repulsive force (if put N to N). This is because there is a demagnetizilng field when put N to N.

[FriedChicken]

The magnet will spin faster when it is repelled, and slower when it is being attracted.

 

That's my hypothesis.