The magnetic field lines for a solenoid look like this:

As one can determine from the right-hand rule, the left side of the diagram contains the north pole and the right part the south pole. It makes sense to me that, near the north pole, the north pole of another magnet would move towards the solenoid's south pole. However, can somebody explain why the magnetic field lines inside the solenoid point towards the north pole? Does this mean if another magnet's north pole was placed inside, it would be attracted to the north pole of the solenoid?


marked as duplicate by sammy gerbil, Yashas, ZeroTheHero, John Rennie, Kyle Kanos Apr 4 '17 at 10:10

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    $\begingroup$ This happens inside a bar magnet too. What's so wrong with it? The exterior field is used to determine the pole. $\endgroup$ – Yashas Apr 4 '17 at 1:39
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    $\begingroup$ Possible duplicate of Does the direction of magnetic field in a solenoid point from north to south anywhere? $\endgroup$ – sammy gerbil Apr 4 '17 at 1:44
  • $\begingroup$ @James Ko The answer is: it is so because Nature has made it like that. There's no "why" here. Everywhere a "why" question cannot be asked, you'll have to take some things for granted. $\endgroup$ – Wrichik Basu Apr 4 '17 at 5:50

It is believed that magnetic monopoles do not exist [there is a lot of debate going on, one research group even claimed to have detected magnetic monopoles].If magnetic monopoles do not exist, then the divergence of the magnetic has to be zero [to make the flux over any closed surface zero]. This is possible only if magnetic field lines form closed loops [you see there is no other magnetic "charge" where the lines can terminate]. So, inside a solenoid or bar magnet, the field has to be opposite to its direction outside. This can be even tested by placing a magnetic compass inside.


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