# When particle is projected perpendicularto magnetic field it travels in circular path in which kinetic energy is constant and momentum changes why? Both should change b'coz velocity changes in circular path

SAGAR SINGH - IIT DELHI
879 Points
12 years ago

Dear rohit,

The magnetic field (B) is an uniform stationary magnetic field for our consideration in the module. It means that the magnitude and direction of magnetic field do not change during motion. The charged particle, however, is subjected to magnetic force acting side way. The direction of motion of charged particle, therefore, changes. In turn, the direction of magnetic force being perpendicular to velocity also changes. Important point to underline here is that this loop of changing directions of velocity and magnetic force is continuous. In other words, the directions of both velocity and magnetic force keeps changing continuously with the progress of motion.

If the span of magnetic field is sufficient around the charged particle, then it will describe a circular path as magnetic force is always perpendicular to the motion. The magnetic force provides the centripetal force required for circular motion. The span of magnetic field around charged particle is important.