Question

A long straight wire carries a current i. A particle having a positive charge q and mass m, kept at a distance Xo(read as X not) from the wire, is projected towards it with a speed v.find the minimum separation between the wire and the particle.

Answer 1

i did it as follows -
let P be the location of the charged particle. the minimum distance is when slope is zero.
therefore dx/dt=0
F=qv X B
\[F=q(Vx i^ + Vy j^) X (-\mu i/2\pi x) k^\]