Question

What is the path followed by a charge entering a uniform magnetic field with its initial velocity along the direction of the magnetic field?

• A. Circular path
• B. Parabolic path
• C. Straight line
• D. Helical path

Hint:

For motion of a charged particle in a magnetic field, the path depends on the angle between the velocity and the magnetic field. If the velocity is parallel to the magnetic field, the path is a straight line.

Answer 1

The Correct Option is C

When a charged particle enters a uniform magnetic field, the direction of the magnetic force is perpendicular to the velocity of the particle. The magnetic force causes the particle to move in a circular or helical path if the velocity has a component perpendicular to the field. However, if the initial velocity is parallel to the magnetic field (i.e., along the direction of the magnetic field), the magnetic force will be zero because the angle between the velocity and the magnetic field is \( 0^\circ \), and thus: \[ F = qvB \sin \theta = qvB \sin 0^\circ = 0 \] Since no magnetic force acts on the particle, it will continue to move in a straight line along the direction of the magnetic field.