$\vec{F}=q(\bar{v} \times \vec{B}) \quad \text { or, } \quad F=q v B \sin \theta$

$(i)$ When $\theta=0^{\circ}, F=q v B \sin 0^{\circ}=0$

$(ii)$ When $\theta=90^{\circ}, F=q v B \sin 90^{\circ}=q v B$

$(iii)$ When $\theta=180^{\circ}, F=q v B \sin 180^{\circ}=0$

This implies force acting on a charged particle is non-zero, when angle between $\bar{v}$ and $\bar{B}$ can have any value other than zero and $180^{\circ} .$