Imagine a solenoid generating a magnetic field. Can this field be focused so that it exists only in a certain section of that solenoid at a given time. If a typical solenoid looked like:
... and then had current applied and generated a field around it:
I would like to adjust, say, a dial all the way to left to generate a field like:
... and then dial it to the right:
... or anywhere in between:
Is this possible with a single solenoid, or would I have to use a number of different solenoids each given current independently?