I am trying to create a powerful magnetic field using coil, and possibly some ferromagnetic metal bars.
The white box with the X on it, is empty, or made of air.
Saying that I have no limits on how many metal bars I have, or their dimensions, but I have limited copper wire length that I can use, and through all examples, the current that I use is constant.
The examples in the image included, but I would gladly accept anything new you can think of, what is the best way to have the maximum possible magnetic flux go through the box?