electromagnet's strength
From the question comments:


  "... on the coil of wire the side that connects with positive is south pole ...". 


This is not correct. The direction of the magnetic field depends on the direction of the current around the axis - not along the axis.


  So then if i finish one full loop all the way across the ferromagnetic core, so iron, this will also have a posative and negative just not alternating. And then if we have a full loop, then another loop starting from the end right over to the beginning then to the end looping, will this change, weaken, or affect the already set north and south poles?


A better way of saying it is, "So if I finish one full layer of the winding and then start a second layer at the end of the first and running back towards the start of the first ...". Provided you keep turning in the same direction around the axis you will be fine. That is how machine-wound coils are made.



See this YouTube video for an example.