Direction of magnetic field inside infinite slab

AI Thread Summary
The discussion focuses on determining the direction of the magnetic field inside a thick slab with a current density J directed along the x-axis. While it is clear that the magnetic field outside the slab points left above and right below, there is confusion about the field's behavior inside the slab. The user acknowledges that Ampere's law indicates a magnetic field must exist inside due to the net current enclosed. Clarification is sought on how to visualize and understand the magnetic field direction within the slab. Understanding this concept is essential for applying Ampere's law correctly in this scenario.
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Suppose we have a thick slab with a current density J pointing strictly in x direction...see below link for figure:

http://teacher.pas.rochester.edu/PHY217/LectureNotes/Chapter5/LectureNotesChapter5056.jpg

what is direction of magnetic field inside?


It is easy for me to see that outside, above the slab, it points to the left, and below it, the field points to the right. I get this by visualizing the J as a bunch of current carrying wires all carrying current in +x direction. But using this idea, I think that insidem the field should cancel, although I know that Ampere's law clearly says that there must be a field since there is a net current enclosed...

If someone could walk me through understanding the direction of the field inside, I would really appreciate it!
 
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