The force on a charged particle is moving in a magnetic field is maximum when the angle between direction of motion and field is

When a charged particle is moving in a magnetic field perpendicular to direction of field, then force acting on charge is maximum.

$\mathrm{F}=\mathrm{Bil} \sin \theta \Rightarrow \mathrm{F}=\mathrm{Bi}1 \sin {90}^{\circ }=\mathrm{Bi}1$