Question

Which of the following particles will experience minimum magnetic force when projected with the same velocity perpendicular to magnetic field in the same magnetic field?

• A. $\alpha -$particle
• B. Proton
• C. ${\text{Be}}^{3+}$
• D. ${\text{Li}}^{2+}$

Answer 1

The correct option is B Proton

Force on a charged particle of charge $q$ moving in a magnetic field $\overrightarrow{B}$ with velocity $\overrightarrow{v}$ is given by$$\overrightarrow{F_m}=q(\overrightarrow{v}\times \overrightarrow{B})$$So,

$F=qvB\sin \theta =qvB\sin {90}^{\circ }=qvB$

For the same speed and the same magnetic field,

$F\propto q$

Minimum the charge, minimum is the magnetic force on the charged particle.

Therefore, magnetic force on the proton is minimum.