Question

When a proton moves in a uniform magnetic field, the momentum change but its kinetic energy does not change because :

• A. The magnetic force exerted will be perpendicular to the direction of motion of the proton.
• B. Work done will be zero.
• C. Kinetic energy does not change.
• D. All

Answer 1

Answer: (D)

All

The magnetic force exerted will be perpendicular to the direction of motion of the proton. As we know when when force acting is perpendicular to the direction of moving charge, work done will be zero. It means kinetic energy does not change. The force is able to change the direction (velocity) of the proton but not its speed (magnitude). Thus momentum and velocity changes.