CBSE 2025 · Region 4 · Set 2 · Q23 · 3 marks

(a)

A charged particle $\displaystyle q$ moving with a velocity $\displaystyle \vec{\mathrm{v}}$ is subjected to a uniform magnetic field $\displaystyle \overrightarrow{\mathrm{B}}$ acting perpendicular to $\displaystyle \overrightarrow{\mathrm{v}}$. If a uniform electric field $\displaystyle \overrightarrow{\mathrm{E}}$ is also set up in the region along the direction of $\displaystyle \overrightarrow{\mathrm{B}}$, describe the path followed by the particle and draw its shape.

(b)

How will the magnetic field inside a long solenoid be affected when :

(i)

the radius of the turns of the solenoid is increased,

(ii)

the length of solenoid as well as the total number of its turns are doubled?

CBSE Class 12 Physics past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.