A magnetic field strength drops-off quickly as the distance from a magnet increases.
Is there any way to use electromagnetic fields to create a magnetic field at a location. For example, if there are strong electromagnetic fields intersecting at a location from many strong transmitters, could a constructive interference be created which creates a local magnetic field?
The engineering idea is that if you create an array of radio transmitters at a strong strength working together, could there be a interference pattern at a point far from the transmitters (maybe 100 meters away) where the fields produce a magnetic field at that location.
I think this could be done as a EM field is composed of a electric field and a magnetic field, shouldn't there be a way to make the magnetic field strong at a location in space.
A positive consequence of this would be that a magnetic placed at that location 100 meters away could be moved by the field. Also, if the field was alternating, rather than steady, then a electromagnet at that location could be alternating, and the force on the electromagnet could provide motive force.
I guess since I have never heard of this, it cannot be done. But then again, it was once said that levitating a normal magnet could not be done, then someone did it with a spinning magnet which levitates above another magnet, now it is a popular toy. The reason it works is that the magnet is spinning so that it cannot flip over. See spin stabilized magnetic levitation.
— Update
Hi, I would like to clarify, I wish to move a physical object, a small magnet at a distance, not to transmit power to the object. Thanks!
— Update 2
My engineering goal for this is a small magnetic, spin stabilized, being pushed from a distant location. A small spin stabilized magnet pushed from below by some "projected" magnetic field could potentially overcome the force of gravity. Imagine a thin lightweight spinning disk with a magnet in the center. If a projected magnetic field is pushing it upwards then it would stay stable and could be projected from ground into space.
This might be done with an array of thousands of transmitters on the ground, somewhere in the desert far away from people. All transmitters could focus a small magnetic field at this magnet.
Alternatively, if the magnetic field alternates with a frequency, then the magnet in the levitated device could also be alternating via electromagnetism, it could be powered by an battery or microwave power transmitted to the object. This is more or less an engineering problem if there is some basic science which can allow this to be a potential reality.
— Update 3
Could "Radiation Friction" be used?
https://physicsworld.com/a/radiation-friction-could-make-huge-magnetic-fields-with-lasers/
Best Answer
This is possible, it's just very very difficult to do.
People regularly do this with the electric field of light to move dielectric particles (insulators) in the lab, and the technique is known as "optical tweezers":
http://en.wikipedia.org/wiki/Optical_tweezers
The reason you don't want to try this with magnetic particles is that the magnetic field of light is much weaker than the electric field, or rather that it doesn't interact very much with most magnetic materials.
Greg's answer above is half correct - The fact that these fields oscillate in time means that the applied force would oscillate as well, however, the field gradient is exploited instead to make optical tweezers work.