Editing magnetic fields Is it possible to control magnets in this way?
Is it possible to:
- Force magnetic field lines to follow specific paths
- Change the number of loops precisely
Also, is it possible for a magnet to have just one loop?
 A: Is it possible to force magnetic field lines to follow specific paths?
To some degree, yes. You can do it with ferromagnets, or superconductors. A piece of iron stuck across the poles of a horseshoe magnet, for example, will confine the magnetic flux inside itself, preventing the magnet from effectively sticking to anything else. And superconductors will pin magnetic fields into flux tubes surround by current vortices.
It is also possible, though computationally difficult, to design configurations of electromagnet coils to produce specific magnetic field shapes in free space, rather in the interior of a solid.
Is it possible to change the number of loops precisely?
"Number of loops" isn't really a thing, because magnetic field lines aren't really a thing. The magnetic field is not actually discretized that way. It's a continuous vector field, with an infinite number of "lines" traversing it at any field strength. The idea of discrete magnetic field lines is just a useful abstraction; if you choose to use it, you have to understand that each line represents a certain arbitrary unit of flux, and then you can look at how the lines you have chosen to trace through the vector field diverge or converge, producing lower or higher local flux densities, to see how the field strength changes in different regions. However, it is perfectly possible to precisely control the field strength.
So, is it possible to have just one loop? Sure. Just measure the strength of the magnet, define that to be the unit you associate with one field line in your diagram. That'll give you exactly one line. Now, just design your magnet to produce a simple field without any torsion in it, so every field line makes exactly one loop through the dipole, and there you go: you've got a field with one line, making one loop.
