A direct current flowing through tbe winding of a long cylindrical solenoid ofradius R produces a uniform magnetic induction B in it. An electron travelling at velocity v enters into tbe solenoid along the radial direction between its turn at right angles to the solenoid axis. After a certain time tbe electron deflected by magnetic field leaves the solenoid. Calculate the time which the electron spends inside the solenoid.

Answer

`[(2m)/(eB) tan^(-1) ((eBR)/(mv))]`