Q. Consider the following statements regarding a charged particle in a magnetic field (i) starting with zero velocity, it accelerates in a direction perpendicular to the magnetic field (ii) While deflecting in the magnetic field, its energy gradually increases (iii) Only the component of magnetic field perpendicular to the direction of motion of the charged particle is effective if deflecting it (iv) Direction of deflecting force on the moving charged particle is perpendicular to its velocity. Of these statement
A) (ii) and (iii) are correct
B) (iii) and (iv) are correct
C) (ii) . (iii) and (iv) are correct
D) (i). (ii) and (iii) are correct
Explanation
(b) In magnetic field, the force on charged particle $\overrightarrow{F} = q\left( \overrightarrow{v}\ \times \overrightarrow{B} \right).$ When particle is at rest in magnetic field the force on it is zero, hence no acceleration. When charged particle is deflected by the magnetic field, its speed does not change but direction of velocity changes because the deflecting force acts perpendicular to $\overrightarrow{v}\ $and $\overrightarrow{B}.\ $The component of magnetic field perpendicular to the direction of motion is effective in deflecting the particle.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.