hey all, this is confusing me a lot: consider an infinitely long cylinder of cross-section radius R. we choose symmetry axis of the cylinder as the z-axis. The cylinder carries a uniform current density J in the +z direction throughout it's cross section. what is B at r inside of the cylinder? Express you answer in the component form B = Bx i + By j + Bz k ...what i'm confused about is whether or not I can use ampere's law with an amperian loop inside the cylinder or if i have to use Biot-Savart..... i did it using ampere's law and i got |B| = uJs/2 ....and the vector B is in the phi direction.....wrapping around the z-axis.......did i do that right? how do i get it into cartesian coords? Do i have to use Biot-Savart in to be able to get it in cartesian coords regardless of whether or not ampere's law can be used?