Physics - Magnetism Question with Solution | TestHub

The magnetic force on a charged particle moving in a magnetic field is given by $\vec{F}=q(\vec{v}\times \vec{B})$.

The magnitude of this force is $F=qvB\sin \theta$, where $\theta$ is the angle between the velocity $\vec{v}$ and the magnetic field $\vec{B}$.

Since the particle is moving along a magnetic field line, its velocity is either parallel or anti-parallel to the magnetic field.

Thus, the angle $\theta$ is either $0^{\circ }$ or $180^{\circ }$.

In both cases, $\sin \theta =0$.

Therefore, the magnetic force acting on the particle is zero.

Answer: Zero.