i have no idea how to do this problem: a velocity selector consists of electric and magnetic fields described by the expressions E=E(k hat) and B=B(j hat), with B=14.5 mT. Find the vale of E such that a 828-eV electron moving along the positive x axis is undeflected. hmm..since it is undeflected we can say that qE=qvB, right? and v=E/B... but how could u solve for E? and how does the 828 eV electron fit into this problem?