When a moving charge carrier in a conductor is under the influence of a magnetic field B , the carrier experiences a force perpendicular to the direction of motion and the magnetic field, resulting in a gyratory path, which is circular in the absence of any other external force. When an electric field E is applied in addition to the magnetic field and perpendicular to that field, this gyratory motion is driven by the electric field, leading to a net drift in the direction E × × B around the guiding center and a lack of mobility in the direction of the electric field. The charge carrier undergoes a helical motion whereby a charge carrier at rest acquires motion in the direction of the electric field according to Coulomb's law, gains a velocity perpendicular to the magnetic field, and subsequently is pushed in the direction v × × B due to the Lorentz force (as v is in the direction of E , v × × B is initially in the same direction as E × × B .) The motion will then oscillate backwards against the electric field until it again reaches a velocity of zero in the direction of the electric field, before again being driven by the electric and magnetic fields, forming a helical path. As a result, in a vacuum, no net current is possible in the direction of the electric field. Likewise, when there is a dense material with a high frequency of collisions between the charge carriers and the conductive medium, mobility is very low and the charge carriers are basically stationary.