JEE Main 2022 — Magnetic Effects of Current Question with Solution

When a charged particle moves in an electric field, the field applies an electric force $\left(\overrightarrow{F}=q\overrightarrow{E}\right)$ along the field, so work done by electric field is non-zero resulting in accelerated motion, thus kinetic energy changes.

When a particle moves in a uniform magnetic field, the force due to magnetic field on it is perpendicular to its velocity, as force  $\left(\overrightarrow{F}=q\overrightarrow{v}\times \overrightarrow{B}\right)$.
Since the magnetic field is constant, so force is constant. So, its direction of velocity constantly changes, but magnitude of velocity remains same. Hence, kinetic energy also does not change.

 Electric field accelerates the particle in the direction of field $\left(\overrightarrow{F}=q\overrightarrow{E}=m\overrightarrow{a}\right)$and magnetic field accelerates the particle perpendicular to the field $\left(\overrightarrow{F}=q\overrightarrow{v}\times \overrightarrow{B}=m\overrightarrow{a}\right)$.