A point charge $q$ moving with velocity $\vec{v}$ in a magnetic field $\vec{B}$ experiences a Lorentz force: $\vec{F}=q(\vec{v}\times \vec{B})$

• In magnitude: $F=qvB\sin \theta$
• $\theta$ is the angle between $\vec{v}$ and $\vec{B}$.
• The force is always perpendicular to both $\vec{v}$ and $\vec{B}$.
• If $\vec{v}$ is parallel to $\vec{B}$ ($\theta =0^{\circ }$), $F=0$.