Consider the following statements regarding flow measurement through pipes : 1. The reduction in constriction diameter causes velocity to increase. 2. High velocities in constriction cause low pressures in the system. 3. The reduction in constriction diameter enables lesser accuracy in its measurement. Which of the above statements is/are correct :
- A1 and 2Correct
- B2 and 3
- C2 only
- D1 and 3
Solution
Concept
Venturi principle
Step-by-step solution
1. Smaller diameter → higher velocity (continuity) (true). 2. Higher velocity → lower pressure (Bernoulli) (true). 3. A larger pressure drop makes the measurement easier and more accurate, so "lesser accuracy" is false.
Explanation
The constriction principle increases the pressure difference and so improves sensitivity.
Why the other options are wrong
Statement 3 is the reverse of the truth.
Shortcut
Constriction: v↑, p↓, better sensitivity.
Common mistake
Accepting statement 3.
Correct answer: A) 1 and 2