E$17$M$.2$ Consider the infinite planar charged sheet we discussed in section E$17\mathrm{.}3.$ Reorient the coordinate system in figure E$17\mathrm{.}1$ so that the $x$ axis is vertical and the $y$ and $z$ axes are horizontal, Then use equation E$11\mathrm{.}3$ and what we know of the electric field of a planar charge to argue that the magnetic field of a moving plate must be uniform, horizontal, and parallel to the plate as shown in figure E$17\mathrm{.}1.$