JEE Physics 2023 Question with Solution

Given: A charged particle has one velocity component parallel to magnetic field $B$ and another component perpendicular to $B$.

Find: The path followed by the charged particle.

The component of velocity perpendicular to $B$ experiences magnetic force and produces circular motion.

The component of velocity parallel to $B$ does not experience magnetic force in the direction of the field, so the particle continues to move along the field.

Combining circular motion with uniform motion along the magnetic field gives a helical trajectory whose axis is along magnetic field $B$.

Therefore, the path is a helical path with axis along magnetic field $B$. The correct option is A.

Given: The velocity of the charged particle has both parallel and perpendicular components with respect to magnetic field $B$.

Find: The nature of the path.

A magnetic field exerts force only on the component of velocity perpendicular to the field. This bends the motion into a circle in the plane perpendicular to $B$.

At the same time, the parallel component remains unchanged and carries the particle forward along the direction of $B$.

Because these two motions occur together, the particle neither moves in a straight line nor remains in a single circle. Instead, it advances along the field while revolving around the field direction.

Hence the path is helical, and its axis is along the magnetic field. So the correct option is A.