Which of the following statements is/are true about the principle of Van de Graaff generator ?

Options

A. The action of sharp points.
B. The charge given to a hollow conductor is transfered to outer surface and it distributed uniformly over it.
C. It is used for accelerating uncharged particle.
D. Both (a) and (b) are true.

Answer

To determine which statements are true about the principle of the Van de Graaff generator, let's analyze the working mechanism of the device step by step.

### Step-by-Step Solution:

1. **Understanding the Van de Graaff Generator**:
- The Van de Graaff generator is a device designed to produce high voltages. It achieves this by accumulating electric charge on a large metallic sphere.

2. **Components of the Generator**:
- The generator consists of a large conducting sphere, a pulley system, and an endless belt. The belt moves continuously around the pulley.

3. **Charge Accumulation**:
- As the belt moves, it picks up charges (usually negative charges) from a source. These charges are then transported to the metallic sphere.

4. **Distribution of Charge**:
- Once the charges reach the metallic sphere, they accumulate on its surface. Due to the properties of conductors, the charges will distribute themselves uniformly over the outer surface of the sphere.

5. **High Voltage Generation**:
- The accumulation of charge on the sphere leads to an increase in electric potential, resulting in high voltage. The more charge that accumulates, the higher the voltage achieved.

6. **Principle of Action of Sharp Points**:
- The generator operates on the principle that sharp points can enhance the electric field, allowing for the transfer of charge to the outer surface of the conductor more efficiently.

7. **Conclusion**:
- Based on the above points, we can conclude that the statements regarding the principles of the Van de Graaff generator that mention the uniform distribution of charge on the outer surface and the action of sharp points are true.

### Final Answer:
- Therefore, the correct options regarding the principles of the Van de Graaff generator are A and B, making option 4 the right answer.