Introduction:
The orifice meter is a type of flow meter used to measure the flow rate of fluid through a pipe. It consists of a flat rectangular plate with a small hole, known as an orifice, through which the fluid passes. This question is asking whether the given statement about the orifice meter is true or false.

Explanation:
The correct answer is option 'B', which states that the given statement is false. Let's understand why this is the correct answer.

Orifice Plate:
The orifice meter typically consists of a circular orifice plate rather than a flat rectangular plate. The orifice plate is installed perpendicular to the flow direction and creates a pressure difference across itself. This pressure difference is then used to determine the flow rate of the fluid.

Working Principle:
When the fluid passes through the orifice plate, it experiences a reduction in cross-sectional area, leading to an increase in fluid velocity. According to Bernoulli's principle, this increase in velocity corresponds to a decrease in pressure. The pressure difference across the orifice plate is measured using pressure taps located upstream and downstream of the plate.

Calculation of Flow Rate:
The flow rate through the orifice meter can be calculated using various equations, such as the Bernoulli equation, the continuity equation, and the discharge coefficient. These equations take into account the pressure difference, the properties of the fluid, and the dimensions of the orifice plate.

Advantages and Disadvantages:
The orifice meter has several advantages, including simplicity, low cost, and wide applicability. However, it also has limitations, such as pressure loss, sensitivity to changes in fluid properties, and the need for accurate calibration.

Conclusion:
In conclusion, the orifice meter used for measuring fluid flow does not consist of a flat rectangular plate. Instead, it employs a circular orifice plate. Therefore, the given statement is false.