In a cyclotron, a charged particle:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → undergoes acceleration all the time
In a cyclotron the particle moves on a circular path inside the dees under the magnetic force, and a circular motion always has a centripetal acceleration even at constant speed. In the gap between the dees the electric field also increases its speed. So the particle is accelerating at every instant.
Why the other options are incorrect
Option (1) speeds up inside the dees due to an electric field — Incorrect. The dees are hollow metal boxes that shield their interior from the electric field, so the speed does not change inside them.
Option (3) slows down inside the dees and speeds up between dees — Incorrect. The speed stays constant inside the dees.
Option (4) speeds up between the dees because of the magnetic field — Incorrect. The speed gain in the gap is due to the electric field; the magnetic force is perpendicular to the velocity, does no work and only bends the path.
Note: A similar question was also asked in CUET (UG) 2023 on 14-06-2023 (Slot 2) and on 11-06-2023 (Slot 3).
NCERT Exemplar:
Moving Charges and Magnetism – …
