Question

A charged particle moves through a magnetic field perpendicular to its direction, then

• A. kinetic energy changes but the momentum is constant
• B. the linear momentum changes but the kinetic energy is constant
• C. both momentum and kinetic energy of the particle are not constant
• D. both momentum and kinetic energy of the particle are constant

Answer 1

Answer: (B)

the linear momentum changes but the kinetic energy is constant

Answer 2

When a charge particle enters a magnetic field at a direction perpendicular to the direction of motion, then the path of the motion is circular. In circular motion the direction of velocity changes at every point and the magnitude remains constant. Therefore, **the tangential momentum will change at every point. **

Kinetic energy is given by $\frac{1}{2} mv ^{2}$. Since the magnitude of the velocity remains constant, therefore the kinetic energywill also remain constant.