A charged particle of charge q and mass m enters a magnetic field as shown. Find radius of the circular path and the time spent inside the field. Neglect gravity.

Options

A. `(R pi theta)/(v)`
B. `(R(pi -2 theta))/(v)`
C. `R ((pi + 2 theta)/(v))`
D. `(2 R theta)/(v)`

Answer

B

Explanation

Angle subtended at the centre `= pi - 2 theta` Time spent inside the field. `t= ("arc length")/("speed")`
`=(R(pi - 2theta))/(v)`