Poles of an electromagnet

[Muthuraj R]

Please find the attached picture..
My understanding : Use right hand thumb rule to find the direction of magnetic flux lines when the direction of currents are known. When I have a 'cross', the lines will be in clockwise direction while I have a 'dot', the lines will be in anticlcokwise direction. And as magnetic flux lines start from N pole and end at S pole, i find the N and S poles.. This works only with hollow cylindrical electromagnet, not with solid one.. Where I make mistake?? Please clarify. Thanks.

 

[0xDEADBEEF]

The picture is pretty confusing maybe intentionally. The idea is, that the solid and the hollow electromagnet has the field lines pointing out of the north pole (material) and into the south pole (material). So the question is if the field lines enter or exit the material. The assumption is, that the probe is in the areas without material and where the probes north pole would point, this is causing the confusion, because the probe is located in different places. In case of the hollow magnet one could also argue that there is no north and south pole, because a probe on the outside would see (practically) no field.