A uniform magentic field of induction `B` is confined in a cyclinderical region of radius `R`. If the field is incresing at a constant rate of `(dB)/(dt)= alpha T//s`, then the intensity of the electric field induced at point `P`, distant `r` from the axis as shown in the figure is proportional to :

Explanation

For `r lt R , e = int E.ds , =(d phi_(B))/(dt)`
`E.2pi r =-A((dB)/(dt)), E.2pir = -pir^(2)((dB)/(dt))`
`E = -(r)/(2)((dB)/(dt)), E = -(r )/(2) alpha , (bar(E)) = (r )/(2)alpha`, Ear