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JEE Main2007PhysicsMagnetic Effects of CurrentActual

A charged particle moves through a magnetic field perpendicular to its direction. Then

Options

  1. Athe momentum changes but the kinetic energy is constant
  2. Bboth momentum and kinetic energy of the particle are not constant
  3. Cboth, momentum and kinetic energy of the particle are constant
  4. Dkinetic energy changes but the momentum is constant

Correct answer

A. the momentum changes but the kinetic energy is constant

Step-by-step solution

Magnetic force is perpendicular to the direction of motion of the particle. Therefore no external work is done and the kinetic energy remains constant. The particle undergoes uniform circular motion, however due to change in direction of motion velocity is not constant. So the momentum is not constant, during uniform circular motion. Therefore, option (B) is correct.

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