If a charged particle does not experience any force in a magnetic field, then ________

Magnetic Field:

The force on a particle moving under the influence of a magnetic field is given as,

$$\begin{gathered} \overrightarrow{F}=q\left(\overrightarrow{v}\times \overrightarrow{B}\right) \\ =qvB\sin \theta \end{gathered}$$

Where $q$ is the charge of the particle, $v$ is the velocity of the particle, $B$ is the magnetic field and $\theta$ is the angle between the direction of velocity and magnetic field.

Therefore, we can see that when $v=0$ and $\theta =0$, $F=0$.

Hence, if a charged particle does not experience any force in a magnetic field, then the particle is either at rest or is moving parallel to the magnetic field.