Which principle is the operation of a U-tube manometer primarily based on?

Explanation:

Principle of U-tube Manometer Operation

The operation of a U-tube manometer is primarily based on the principle of hydrostatic equilibrium. This principle states that the pressure at any point in a fluid at rest is the same in all directions. In a U-tube manometer, the pressure difference between two points is determined by the height difference of the liquid column in the two arms of the tube.

Analyzing the Given Options

1. "Venturi effect." (Incorrect)

   • The Venturi effect involves the reduction in fluid pressure that results when a fluid flows through a constricted section of pipe. This is not the principle that a U-tube manometer operates on.

2. "Pascal's law." (Incorrect)

   • Pascal's law states that pressure exerted anywhere in a confined incompressible fluid is transmitted equally in all directions throughout the fluid. While relevant to fluid dynamics, it is not the primary principle behind the U-tube manometer.

3. "Hydrostatic equilibrium." (Correct)

   • Hydrostatic equilibrium is the condition in which a fluid is at rest, and the pressure at any point within the fluid is constant. This principle is the basis for how a U-tube manometer measures pressure differences.

4. "Bernoulli's principle." (Incorrect)

   • Bernoulli's principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in the fluid's potential energy or pressure. This principle is not directly applied in the operation of a U-tube manometer.