Glass stirring rod

A barometer tube is a slender, sealed, and typically transparent tube used in barometers to measure atmospheric pressure. It is usually filled with a liquid, often mercury, but sometimes water or another fluid, which rises or falls within the tube in response to changes in atmospheric pressure. The height of the liquid column in the tube serves as an indicator of the current atmospheric pressure, with higher pressure causing the liquid to fall and lower pressure causing it to rise. This measurement helps in predicting weather changes and understanding atmospheric conditions.

The Bernoulli tube apparatus, also known as a Venturi tube apparatus, is a scientific device used to demonstrate the principles of fluid dynamics, particularly the Bernoulli's principle. It consists of a specially shaped tube with a constricted region, often referred to as a Venturi section. When fluid (liquid or gas) flows through the tube, the constricted section leads to changes in pressure and velocity according to Bernoulli's principle, which states that as the velocity of a fluid increases, its pressure decreases and vice versa. This apparatus is commonly used in educational settings to visually illustrate how the flow of a fluid can affect its pressure, helping to explain various phenomena like lift in aircraft wings, fluid flow through pipes, and more.