In the given arrangement, the space between a pair of co-axial cylindrical conductors is evacuated. The outer cylinder, called anode, may be given a positive potential V relative to the inner cylinder. A static homogeneous magnetic field `vec(B)` parallel to the cylinder axis, directed out of plane of figure is aslo present. induced charges in the conductors are neglected. We study the dynamics of electrons with rest mass m and charge e. The electrons are released at the surface of inner cylinder. Consider the following two cases Case 1: Firstly the potential V is turned on, but `vec(B) = 0`. An electron with negligible velocity is ejected at the surface of inner cylinder. It is found to hit the anode. Case 2: Now V = 0 but `vec(B)` is present. An electron starts out with an initial velocity `vec(v_(0))` in radial direction. For magnetic field larger than critical value `B_(c)` the electron will not reach the anode. Considering the case 1, the trajectory of electron will beA. straight lineB. CircularC. ParabolicD. Helical