A particle having no charge and almost no rest mass

Options

A. neutrino
B. neutron
C. electron
D. positron

Answer

To solve the question, we need to identify which particle has no charge and almost no rest mass from the given options: neutron, positron, electron, and neutron. Let's analyze each option step by step.

### Step 1: Analyze the Positron
- A positron is the antiparticle of the electron and carries a positive charge (+1).
- Since the question specifies a particle with no charge, the positron cannot be the correct answer.

**Hint:** Check the charge of each particle to determine if it meets the criteria of having no charge.

### Step 2: Analyze the Electron
- An electron has a negative charge (-1).
- Similar to the positron, since the question specifies a particle with no charge, the electron is also not the correct answer.

**Hint:** Remember that the question requires a particle with zero charge, so eliminate any options with a non-zero charge.

### Step 3: Analyze the Neutron
- A neutron has no charge; it is electrically neutral.
- However, a neutron has a rest mass of approximately 1.67 × 10^-27 kg, which is not considered "almost no rest mass."

**Hint:** Consider both the charge and mass of the particles to find the one that fits both criteria.

### Step 4: Analyze the Neutrino
- A neutrino is a particle that is electrically neutral (no charge) and has an extremely small mass, often considered negligible or "almost no rest mass."
- Since the question mentions a particle with no charge and almost no rest mass, the neutrino fits this description perfectly.

**Hint:** Look for particles that are known for their negligible mass when considering options.

### Conclusion
Based on the analysis:
- The correct answer is the **neutrino**, as it has no charge and almost no rest mass.

**Final Answer:** Neutrino