Consider a long thin conducting wire carrying a uniform current . A particle having mass "M" and charge "q' is released at a distance "a" from the wire with a speed along the direction of current in the wire. The particle gets attracted to the wire due to magnetic force. The particle turns round when it is at distance x from the wire. The value of x is [ is vacuum permeability] [2025]
(4)

Let the velocity of the particle make an angle with initial direction when it is at a distance x.
... (i)
Also, ... (ii)
... dividing eq (i) with eq (ii)
or
Or