Which of the following cannot be accelerated by applying an electric field?

Options

A. Protons
B. Electrons
C. Neutrons
D. Positrons

Answer

To solve the question "Which of the following cannot be accelerated by applying an electric field?", we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Electric Field and Force**:
- An electric field exerts a force on charged particles. The force (F) acting on a charged particle in an electric field (E) is given by the equation:
\[ F = Q \cdot E \]
where \( Q \) is the charge of the particle.

2. **Relate Force to Acceleration**:
- According to Newton's second law, the acceleration (a) of a particle can be expressed as:
\[ a = \frac{F}{m} \]
where \( m \) is the mass of the particle. Substituting the expression for force, we get:
\[ a = \frac{Q \cdot E}{m} \]

3. **Identify the Charge of Different Particles**:
- Protons have a positive charge.
- Electrons have a negative charge.
- Positrons (the antimatter counterpart of electrons) have a positive charge.
- Neutrons have no charge (they are neutral).

4. **Determine Which Particles Can Be Accelerated**:
- Since acceleration depends on the charge of the particle, we analyze each:
- Protons (charged) can be accelerated.
- Electrons (charged) can be accelerated.
- Positrons (charged) can be accelerated.
- Neutrons (neutral) cannot be accelerated because they have no charge.

5. **Conclusion**:
- The particle that cannot be accelerated by applying an electric field is the neutron.

### Final Answer:
The particle that cannot be accelerated by applying an electric field is the **neutron**.

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