Aproton, moving in a uniform magnetic field, moves in a circle perpendicular to the field lines and takes time t for each circle. if the proton's speed tripled, what would now be its time to go around each circle? 42) a) 9t b) t c) 3t d) t/9 e) t/3 b

option (B)

Explanation:

mass of proton, m = m

charge of proton, q = e

Time period, T = T

Initially the speed of proton is v.

The time period of the proton when it is moving in magnetic field perpendicular to the direction of magnetic field is given by

Where, r be the radius of circular path.

The relation between r and the speed v is given by

Where, B be the strength of magnetic field. Substitute this value of r in the expression of time period

Here, we observe that the expression for the time period is independent to v and r so, as we change the velocity, the time period remains same.