Explanation:


To understand why the correct answer is option 'B', let's first understand what an orifice type viscometer is and how it works.

An orifice type viscometer is a device used to measure the viscosity of a fluid. It consists of a small orifice through which the fluid flows. The pressure drop across the orifice is measured, and this pressure drop is related to the viscosity of the fluid.

How does it work?

When a fluid flows through an orifice, it experiences a pressure drop due to the resistance offered by the orifice. This pressure drop is directly proportional to the viscosity of the fluid. The relationship between the pressure drop and the viscosity is given by the Hagen-Poiseuille equation, which states that the pressure drop is proportional to the viscosity, flow rate, and the dimensions of the orifice.

Converting viscosity to pressure:

The pressure drop across the orifice can be measured using a pressure gauge. By measuring the pressure drop, we can determine the viscosity of the fluid using the Hagen-Poiseuille equation. The equation can be rearranged to solve for viscosity:

Viscosity = (Pressure Drop * Flow Rate * Orifice Constant) / (Density * Orifice Area)

From this equation, it is clear that the viscosity is directly proportional to the pressure drop. Therefore, by measuring the pressure drop across the orifice, we can convert the viscosity of the fluid.

Why is pressure the correct answer?

The viscosity of a fluid is a measure of its resistance to flow. This resistance is manifested as a pressure drop when the fluid flows through an orifice. Therefore, by measuring the pressure drop, we can determine the viscosity of the fluid. The other options (force, displacement, and potential difference) are not directly related to viscosity and cannot be used to convert viscosity in an orifice type viscometer.

In conclusion, the correct answer is option 'B' - Pressure. By measuring the pressure drop across the orifice in an orifice type viscometer, we can convert the viscosity of the fluid.