Cottrell precipitator is used

Options

A. To prepare high quality emulsions
B. To precipitate smoke
C. In purification of water
D. To remove excessive fog for safe landing of
aeroplanes

Answer

### Step-by-Step Solution:

1. **Understanding Cottrell Precipitator**:
- The Cottrell precipitator is an electrostatic device designed to remove particulate matter from gases. It operates by using electrical charges to attract and collect dust particles or fumes.

2. **Mechanism of Action**:
- The device consists of a positively charged wire and walls that act as electrodes. The negatively charged dust particles are attracted to the positively charged surfaces, allowing for their collection.

3. **Applications of Cottrell Precipitator**:
- **Purification of Dust Particles**: The primary function of the Cottrell precipitator is to purify air by removing dust particles.
- **Removal of Sulfuric Acid Mist**: It is effectively used in industries to eliminate sulfuric acid mist from the air.
- **Cement Industry**: The device is utilized to remove cement mill dust, which is a common pollutant in cement production.
- **Metallurgical Applications**: It is also used in metallurgy to capture fumes generated during the processing of various metals.

4. **Evaluating Options**:
- **Option A**: Prepare high-quality emulsion - Incorrect, as the Cottrell precipitator does not form emulsions.
- **Option B**: To precipitate smoke - Correct, as it is used to purify dust particles and precipitate smoke.
- **Option C**: In purification of water - Incorrect, as it is not used for water purification.
- **Option D**: To remove excessive fog for safe landing of airplanes - Incorrect, as it has no application in aviation.

5. **Conclusion**:
- The only correct application of the Cottrell precipitator from the given options is to precipitate smoke.