Correct Option: B  [ To measure the velocity and to find the direction of wind. ]
Remark:
Explanation: An anemometer is a meteorological instrument used to measure wind speed and direction. It is an essential tool in weather stations, aviation, and marine forecasting.
Working Principle: The cup anemometer has three or four cups that rotate with the wind. The rotation speed is proportional to wind velocity. Advanced types also detect wind direction.
Types of Anemometers:
- Cup: Measures wind speed using rotating cups.
- Vane: Measures both speed and direction.
- Hot-wire: Uses heat loss to measure air flow.
- Ultrasonic: Uses sound waves for precise measurement.