Question

The venturi-meter works on:

• A. The principle of perpendicular axes
• B. Huygen's principle
• C. Bernoulli's principle
• D. The principle of parallel axes

Answer 1

The Correct Option is C

A venturi-meter is a device used to measure the flow rate or velocity of a fluid through a pipe. It operates based on Bernoulli's principle, which states that an increase in the speed of a fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy. The principle relates the velocity of the fluid to the pressure difference between two points.

Here's how it works: 

1. The venturi-meter consists of a converging section, a throat, and a diverging section. As the fluid enters the narrower throat, its velocity increases and, according to Bernoulli's principle, the pressure decreases.
2. The difference in pressure between the wider section and the throat is measured using a manometer or pressure sensors.
3. Using the known dimensions of the meter and the fluid properties, the flow rate can be calculated using Bernoulli’s equation:

P₁ + 0.5ρv₁² + ρgh₁ = P₂ + 0.5ρv₂² + ρgh₂

Where:

• P₁, P₂ = fluid pressures at the wider section and throat, respectively
• v₁, v₂ = fluid velocities at the wider section and throat
• ρ = fluid density
• g = acceleration due to gravity
• h₁, h₂ = heights above a reference point (often neglected for horizontal flow)

The flow rate can then be determined by rearranging the equation to solve for the velocity and subsequently the volumetric flow rate.

Bernoulli's principle is thus crucial for the operation of a venturi-meter, as it relates pressure differences to fluid dynamics, enabling the calculation of flow rates accurately.