# Motion angular to the magnetic field

Yet we asumed, the electron motion is entire perpendicular to the magnetic field. How does the trajectory of the electrons change, when they enter the magnetic field angular with an angle $\delta$ against the magnetic field?
We rotate the cathode ray tube and observe with a constant magnetic field B:With constant acceleration voltage Va the following pictures are visible:The electrons move on helix trajectories. Reason therefor is, that the inital speed v0 is not perpendicular to the magnetic field B. So beside the perpendicular component $v_{\perp}$ there is a parallel component $v_{\parallel}$. $v_{\perp}$ causes the orbital motion, $v_{\parallel}$ causes a motion in the direction of the magnetic field. So the electrons drift on a helix trajectory.