Problem 3.353

A thin wire ring of radius $a$ carrying a charge $q$ approaches the observation point $P$ so that its centre moves rectilinearly with a constant velocity $v$. The plane of the ring remains perpendicular to the motion direction. At what distance $x_{m}$ from the point $P$ will the ring be located at the moment when the displacement current density at the point $P$ becomes maximum? What is the magnitude of this maximum density?