Question

Which of the following particles will experience maximum magnetic force (magnitude) when projected with the same velocity perpendicular to a magnetic field?
(a) Electron
(b) Proton
(c) He⁺
(d) Li⁺⁺

Answer 1

(d) Li⁺⁺

Force on a moving charged particle,
F = qVBsin$\theta$
​As velocity V and magnetic field B are constant, and angle between the magnetic field and charged particle is $90°$, the only thing on which force F depends is charge q.
Now, the charge on $L{i}^{++}$ > charge on electron, proton or $H{e}^{+}$. So the force is maximum for $L{i}^{++}$.