The variable area meter consists of which of the following features?

The variable area meter operates on the principle of changing the area of flow in relation to the flow rate of a fluid. In this device, the fluid flows through a tapered tube, where the diameter gradually decreases along its length. As the fluid moves from the bottom to the top of the tube, the geometry of the tapered design allows for the fluid velocity to change based on the flow rate.

When the flow rate increases, the fluid must travel faster to maintain the same volume of flow through the constricted area. This flow behavior causes the float, typically positioned within the tube, to rise higher in the tapered section. The rise of the float corresponds to an increase in flow rate, and the height of the float provides a visual indication of the flow measurement.

This design effectively translates the variable area created by the tapered tube into measurable flow values, which is integral to the operation of a variable area meter. Therefore, stating that the correct answer reflects the fluid flowing through the tube from the bottom to the top accurately describes how the device functions in measuring flow rates.