Question

Low air velocity will be measured by

• A. Kata thermometer
• B. Globe thermometer
• C. Wet thermometer
• D. Beckmans thermometer

Hint:

Think of a heated-alcohol thermometer whose cooling rate reveals the speed of air movement.

Answer 1

The Correct Option is A

Step 1: Understand what is being measured. The question asks for the instrument used to measure low air velocity (air current/air movement at low speeds), which is an important parameter in environmental hygiene and occupational health settings.

Step 2: Know the Kata thermometer. The Kata thermometer is a heated-alcohol thermometer. The large bulb is heated to above 38 degrees C, and the time taken for the alcohol column to fall from 38 degrees C to 35 degrees C is noted. This cooling time is used to calculate air current speed. It is specifically designed and validated for measuring low air velocities in studies of air circulation (e.g., inside buildings, mines, factories).

Step 3: Eliminate other options. Globe thermometer measures radiant heat (mean radiant temperature) and is used in the calculation of Wet Bulb Globe Temperature (WBGT). Wet thermometer (wet bulb thermometer) measures humidity and is part of hygrometers. Beckmans thermometer is a differential thermometer used for precise measurement of temperature differences, not air velocity.

Conclusion: The Kata thermometer is the correct instrument for measuring low air velocity.