Equipment:

• Air blower
• Venturi tube
• manometer

Demo:

This demonstration is shown in the picture to the left. A glass tube with large and small diameter sections and outlets for measuring pressure at two points is attached to the stand. An air blower creates air flow through the tube.

Explanation:

The velocity of the air is higher in the narrow section and lower in the wide section of the tube which creates the pressure difference (see picture to the right). The pressure difference p(large diameter)-p(small diameter) is also equal to ρgh. h is the difference in liquid level.