Is it possible to track changes in a non-static magnetic field? How strongly does diamagnetism work in relation to magnetism? Can you ‘tune’ a magnet to produce a set amount of attraction or repulsion over a set distance?
–Tim
Scratch that, can you tune a magnet to produce a dynamic amount of attraction or repulsion over a constantly varying distance in direct relation to measured changes in the magnetic field?
::sigh:: I need to be more specific but I don’t want to give away my ideas!
So, patent pending on all ideas and inventions offered during this discussion. And yes, I’m serious.
–Tim
So, anybody in the day crowd know any of this?
–Tim
I realize you don’t want to be too specific … so my ideas are probably not too helpful, since I might be missing what you’re getting at.
By ‘tuning the magnet’, you really only need to tune the field, right? There’s a couple ways I could think of to do that – vary the strength of a mechanically fixed field, or vary the position of a permanent magnet (e.g. rotate it depending on what strength of field you want.)
This seems like just a simple control system – you have some sensor to measure the field wherever it is you need to measure it, plus the varying distance has to be taken into account – put these together to figure out how to modify the field. You just have to make sure it’s stable.
I guess the big question is how is the field going to be changing?
Just random thoughts … this sort of makes me think of the way some power meters use eddy currents on the metal disk to get an accurate adjustment to torque on a motor to do their measurement.
When you say “comparing diamagnetism to magnetism”, I presume that by “magnetism” you mean ferromagnetism, the effect which causes iron to be attracted to a magnet? Both forces are directly proportional to the strength of the magnetic field, and which is stronger depends soley on the material. In other words, iron or nickel (both ferromagnetic) will be attracted to a magnet, at any distance, and water and copper (both diamagnetic) will be repelled by a magnet at any distance. Usually, when you’re balancing an attractive force with a repulsive one, one of the forces is gravity or an electrostatic force. Both gravity and monopolar electrostatic forces (the simplest sort) fall off as the inverse square of the distance, while dipolar magnetic fields fall off as the inverse cube of the distance, so you can balance them. For instance, if you have a magnet with a positive electric charge on it, and a piece of copper with a negative electric charge on it, then there’ll be an equilibrium distance where the two forces balance. You could adjust this distance by changing the strength of your magnet and the charge on the objects. You could also do this with like charges and a ferromagnetic material like iron, but then the equilibrium would be unstable, which you probably don’t want.
As to tracking changes in a magnetic field, there’s two ways you could do this. The simplest is just to continually measure the magnetic field with a compass, and watch how it changes. If you want to get fancy, though, a changing magnetic field produces an electric field, and you could measure that, instead.
Chronos, thank you. That was exactly what I was looking for. I am applying to the Ewing Marion Kauffman Foundation for a grant to patent and develop some magnetic technologies I have devised. Would you be adverse to my emailing you privately a detailed description of these devices so that you could help me a bit with them? I would appreciate it very much.
By magnetism I do indeed mean ferromagnetism. By ‘tuning’ a magnetic field, though, what I mean is would it be possible to create a magnetic field that can dynamically vary dependant upon the strength and distance of the opposite polarity by increasing or decreasing the voltage, amperage, or current applied to the electromagnet. By doing so I would hope to create equilibrium between the forces where the distance between the two is constantly changing.
panamajack, as for tracking the changes, this would be a three dimensional field, not a plane, therefore I would think a compass would be ill equipped considering we would be tracking a multitude of objects and directions. What about a series of lasers that could track the changes by the bending and refracting/reflecting of the light on various wavelengths? Perhaps a magnetic-gyroscope, even?
And if they do approve a grant, I would certainly need people who are very good with physics, lasers, electronics, and magnetics to work with me on developing these applications, if you or anyone here would know how to find and contact such people.
So ferromagnetism is the tendancy for a ferrous metal to be attracted to a magnetic source regardless of it’s polarity, electromagnetism is the tendancy for a material to be attracted or repulsed by a magnet dependant on it’s polarity, and diamagnetism is the tendancy for certain materials to be repulsed by a magnet regardless of it’s polarity? Just making sure I have all four planes laid out correctly.
A final thought… how large is the magnetosphere’s influence on our perceived weight? Do our current calculations of the strength of Earth’s gravity take into account the diamagnetic effects of the magnetosphere?
–Tim
Homer, the term you need to do a search on for measuring magnetic fields is magnetometer. A simple one you can build yourself is just three coils of wire, with the planes of the coils mutually perpendicular to one-another. These sense changes in the magnetic field, so you need to integrate to get the fields as a function of time.
Sure, you can easily vary the strength of a magnetic field by varying the current through your electromagnet. There’s other ways, too, but the current is usually the easiest.
It’s probably simplest for your purposes if you don’t consider “electromagnetism” as a single effect: Unless you’re changing things rather rapidly, it’s easiest to consider the electrostatic force as separate from the magnetic force. You’re right on ferromagnetism and diamagnetism, but you should replace that statement of “electromagnetism” with a purely electric statement, that the electric force is attractive or repulsive depending on the charges of the objects.
Crudely, to balance monopolar forces (like the simplest electrostatic forces) with dipolar forces (the simplest magnetic forces), you’d say that the monopolar force is more important at large distances, and the dipolar force is more important at small distances.
One word of warning, by the way: Diamagnetic forces are very weak, relative to the more familiar ferromagnetism, so you need a much more powerful magnet to get noticeable diamagnetic effects. This might be enough to make your planned device impractical, unless you have access to superconducting magnets and the like.
And sure, you can e-mail me, if you’d like. That’s why I list my address.