Positively charged particles are projected into a magnetic field. If the direction of magnetic field is along the direction of motion of the charged particles, the particles will experience
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → no change in velocity
The magnetic force on a charged particle is given by: $F = q (\vec{v} \times \vec{B})$
If the velocity $\vec{v}$ is parallel to the magnetic field $\vec{B}$, the cross product is zero: $\vec{v} \times \vec{B} = 0$
Therefore, the magnetic force $F = 0$, and the particles will continue to move in a straight line without deflection.
Answer: No force; particles continue in a straight line and without any change in velocity.