Which of the following particles will describe the smallest circle when projected with the same velocity perpendicular to a magnetic field?

Options

A. Proton
B. Deuteron
C. Electron
D. `alpha`- particle

Answer

C

Explanation

In this case path of charged particleis circular
and magnetic force provides the necessary centripetal force i.e. `Bqv=(mv^(2))/r`
or radius of path `r=(mv)/(Bq)`
Since v ad B wil remain same `r oo m/q`
The ratio is leat for electron. Therefore i will describe the smallest circle.