F IELDS

F IELDS . . Velocity selector You know that a charge q moving with velocity v in presence of both electric and magnetic fields experiences a force given by Eq. ( . ), that is, F = q ( E + v × B ) = F E + F B We shall consider the simple case in which electric and magnetic fields are perpendicular to each other and also perpendicular to the velocity of the particle, as shown in Fig. . . We have, ˆ ˆ ˆ , , E B v E j B k v i