Drift Velocity can be defined as the free moment of the electors in a conductor in the random direction with random velocities.
However, when an external electric field is applied to the conductor then the randomly moving electron will start to move in the direction of the field due to the electric force.
The electric field E = potential difference V / length of conductor L. So drift velocity becomes half of its previous value. "When length is doubled, the drift velocity is halved and the resistance is doubled. Thus, when the length of the conductor is doubled, the drift velocity is halved.
The velocity gained by the accelerating electrons in uniform elactric field inside the conductor is drift velocity. The average velocity , acquired by free electrons along the length of a metallic conductor, due to existing electric field is called drift velocity.
u = μE
(where u is the drift velocity, μ is the electron mobility (with units m2/(V⋅s)) of the material and E is the electric field (with units V/m).)
both poles are same only
i.e. ball will start