Question

An electric field cannot accelerate:
A. electrons
B. photons
C. neutrons
D. $\alpha $- particles

Answer 1

Hint:If a charged particle is present inside an electric field, this field applies a force on the particle thus accelerating it. In this question the electrons, protons and $\alpha $- particles are electrically charged particles whereas neutron is an electrically uncharged particle or possesses zero charge and therefore does not experience a force in the electric field.

Complete answer:
Whenever a charge is present inside the electric field the field exerts a force equal to $F = \dfrac{{k{q_1}{q_2}}}{{{r^2}}}$on the charged particle. This force produces an acceleration in the particle which is equal to F/m, where m is the mass of the particle.

-Electrons are electrically charged with a negative charge of -1.6$ \times {10^{ - 19}}C$.
-Proton is also electrically charged with a positive charge of +1.6$ \times {10^{ - 19}}C$.
-Alpha particles possess a charge of $ + 3.2 \times {10^{ - 19}}C$.

Since all these particles are charged they are accelerated by the applied electric field.Whereas the neutron is electrically neutral and does not contain any charge on it and therefore cannot be accelerated by the applied electric field. Therefore an electric field cannot accelerate neutrons.

Hence, option C is the correct answer.

Additional information:
The region around a charged particle where another charged particle can experience force is known as electric field. The force exerted in an electric field is equal to,
$F = \dfrac{{k{q_1}{q_2}}}{{{r^2}}}$,
where k is the electrical force constant, ${q_1}$ is the charge due to which electric field is created,${q_2}$ is the charge that enters the electric field and r is the distance of separation between the two charges.

Note:The most important point to ponder in this question is for any particle to be accelerated in the electric field it must contain some amount of charge. Neutrons possess no charge and therefore do not experience acceleration due the presence of electric fields.