Question

Which one of the following quantities of a flowing fluid is measured using a rotameter?

• A. Static pressure
• B. Dynamic pressure
• C. Volumetric flow rate
• D. Viscosity

Hint:

- Rotameter = variable area flowmeter. - Directly calibrated for volumetric flow rate. - Common in labs and industries due to simplicity and low cost.

Answer 1

The Correct Option is C

Step 1: Recall the principle of rotameter.
A rotameter is a variable area flowmeter, consisting of a vertically tapered tube and a float.
Step 2: How it works.
- As fluid flows upward, it lifts the float.
- The float rises until the upward drag force equals the downward weight of the float.
- The float’s position indicates the volumetric flow rate directly on a calibrated scale.
Step 3: Eliminate incorrect options.
- Static pressure (A) is measured by pressure gauges, not rotameter.
- Dynamic pressure (B) is measured using a Pitot tube.
- Viscosity (D) is measured using viscometers, not rotameters.
Hence, rotameter measures volumetric flow rate.
\[ \boxed{(C) \; \text{Volumetric flow rate}} \]