Of the Following Thermometers the one which is the most useful for the measurement of a rapidly varying temperature is

To determine which thermometer is most useful for measuring rapidly varying temperatures, we should consider the types of thermometers available and their response times.

1. Mercury Thermometer: Offers good accuracy but can be slow to respond to rapid temperature changes due to the time taken for the mercury to rise or fall in the glass tube.

2. Digital Thermometer: Generally has a faster response time than traditional thermometers. They use electronic sensors to detect temperature, allowing for rapid readings.

3. Infrared Thermometer: Provides instant readings without direct contact and can quickly measure surface temperatures. They are excellent for quickly varying temperatures, especially in applications where rapid changes occur.

4. Thermocouple: Known for their quick response times and is widely used in industrial applications for monitoring rapidly changing temperatures. They can also measure a broad range of temperatures.

Conclusion

Among these options, Thermocouples and Infrared Thermometers are the most suitable for measuring rapidly varying temperatures due to their fast response times. However, for specific applications—like non-contact measurements—an Infrared Thermometer would be preferred, while Thermocouples are better suited for precise industrial applications.