As shown in Fig. 30-8, a particle of charge q enters a region where an electric field

Question:

As shown in Fig. 30-8, a particle of charge q enters a region where an electric field is uniform and directed downward. Its value E is 80 kV/m. Perpendicular to and directed into the page is a magnetic field B = 0.4 T. If the speed of the particle is properly chosen, the particle will not be deflected by these crossed electric and magnetic fields. What speed should be selected in this case? (This device is called a velocity selector.) E = 80 kV/m ||||||||| X X x X +q qvB X X Eq X X V = ? X Fig. 30-8 B = 0.4 T (into page)