The particle that can not be accelerated by van de Graaff generator is:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → neutron
A van de Graaff generator accelerates particles with the electric field produced by its high-voltage shell, and an electric field exerts a force \( F = qE \) only on a charged particle.
A neutron carries no charge, so \( F = 0 \) and it cannot be accelerated. The proton, the \( \alpha \)-particle and the \( \mathrm{He^{+}} \) ion are all charged and can be accelerated.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic was removed from the latest NCERT book (2026-27), and it also appears to be out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Van De Graaff Generator – “This is a machine that can build up high voltages of the order of a few million volts. The resulting large electric fields are used to accelerate charged particles (electrons, protons, ions) to high energies needed for experiments to probe the small scale structure of matter.”