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It's extremely difficult to create a magnetic field that can influence objects 1 m away, and somewhat impossible at 10 m away... Why is that? Why is the magnetic field heavily dependent on distance?

A solenoid, has $I$ flowing and generates $B$.

$B$ is only applied at small distances, by increasing $I$ to infinity(for example) would $B$ expand greatly over large distances? Or would that depend on $n$ of the solenoid?

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Because there are no magnetic charges the simplest system that can generate a magnetic field is a dipole. The field from a dipole (magnetic or electric) falls off as $1/r^3$ rather than $1/r^2$ so the field strength falls off more rapidly with distance than the electric field from a point charge.

Increasing the current or the number of turns will certainly increase the strength of the magnetic field from a solenoid, but you're still stuck with the $1/r^3$ dependance on distance. You might be interested in this article that describes one way of channeling a magnetic field over (relatively) large distances.

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  • $\begingroup$ I read it earlier when you posted it on another question, but the thing is how can this be useful? Could this be used to attract objects from point X to the magnetic source? I doubt the usefulness of this concept, probably from my lack on understanding. $\endgroup$
    – Pupil
    Commented Feb 25, 2014 at 9:37
  • $\begingroup$ @key: it could be used to attract objects to the end of the magnetic pipe. Once the object hit the end of the pipe it would be stuck there - it wouldn't travel down the pipe towards the magnet. $\endgroup$
    – John Rennie
    Commented Feb 25, 2014 at 12:09
  • $\begingroup$ Do you think it's possible to build electromagnet that produces a magnetic field that could apply forces of 1000N+ over 0.101 meters? If so, how massive might it be and how much power do you think it would consume? $\endgroup$
    – Pupil
    Commented Feb 26, 2014 at 19:34
  • $\begingroup$ @Key: I have no idea I'm afraid. $\endgroup$
    – John Rennie
    Commented Feb 27, 2014 at 6:41

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