Use app×
Join Bloom Tuition
One on One Online Tuition
JEE MAIN 2025 Foundation Course
NEET 2025 Foundation Course
CLASS 12 FOUNDATION COURSE
CLASS 10 FOUNDATION COURSE
CLASS 9 FOUNDATION COURSE
CLASS 8 FOUNDATION COURSE
0 votes
321 views
in General by (115k points)
closed by

Which of the following statements are TRUE, when the cavitation parameter σ = 0?

i. the local pressure is reduced to vapor pressure

ii. cavitation starts

iii. boiling of liquid starts

iv cavitation stops


1. i, ii and iv
2. only ii and iii
3. only i and iii
4. i, ii and iii

1 Answer

0 votes
by (152k points)
selected by
 
Best answer
Correct Answer - Option 4 : i, ii and iii

Explanation:

Thoma's cavitation parameter (σ): It is the ratio of Net Positive Suction Head (NPSH) to the total head.

\(\sigma = \frac{{NPSH}}{H} = \frac{{\left( {\frac{{{P_A}}}{{\rho g}} - \frac{{{P_V}}}{{\rho g}} - z - {h_f}} \right)}}{H}\)

NPSH: It is defined as the net head developed at the suction port of the pump, in excess of the head due to the vapour pressure of the liquid at the temperature in the pump. NPSH must be positive for preventing the liquid from boiling. Boiling or cavitations may damage the pump. If NPSH reaches zero then the liquid starts boiling and cavitation starts.

Cavitation: It is defined as the phenomenon of formation of vapour bubbles of a flowing liquid in a region where the pressure of the liquid falls below its vapour pressure and the sudden collapsing of these vapour bubbles in a region of higher pressure. When the vapour pressure collapse, very high pressure is created.

Effects of cavitation:

(i) The metallic surfaces are damaged and cavities are formed on the surfaces.

(ii) Due to the sudden collapse of the vapour bubble, considerable noise and vibrations are produced.

(iii) Due to cavitation, the metal of the runner vanes and the draft tube is gradually eaten away, which results in lowering the efficiency of the turbine.

Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ experts/mentors/students.

Categories

...