7. An infinitely large plate with a thickness dcarries a current with a density Jalong the z-direction. The cross-section of the plate is given in the figures below, with the x, y, z coordinates. (a) [7] When the current density is positive and uniform, 6 (>0), find the direction and magnitude of the magnetic field for the region x magnitude of the field vs x. d/2. Draw the graph of the d/2 -d/2 0 d/2 0 -d/2 X X E OOOOO OOOOO B OOOOO OOOOO O O OOOOO OOOOO Oo. OOOOO OOOOO (b) [8] When the current density linearly varies with x, x) = 2x/d(>0), find the direction and magnitude of the magnetic field for the region x d/2. Draw the graph of the magnitude of the field vs x. OOOOO OOOOO OOOOO O O Oo OOOOO OOOOO OOOO OO OO Jo : J(x) = 2Jox/d