Marot jar facts for kids

A Mariotte jar is a clever device that helps water flow out at a steady speed. It's like a special kind of syphon or siphon, invented way back in the 1700s. The cool thing about a Mariotte jar is that no matter how much water is inside – whether it's full or almost empty – the water always comes out at the same speed and in the same amount. This makes it super useful for experiments or anything that needs a constant flow of liquid.

What is a Mariotte Jar?

A Mariotte jar is a sealed container, usually made of glass, with two pipes. One pipe lets water out from the bottom, and another, shorter pipe lets air in from the top. The secret to its constant flow is how these two pipes work together with air pressure.

How Does a Mariotte Jar Work?

Let's look at the diagram to understand how it works.

Setting Up the Flow

Imagine the jar is filled with water (shown in blue) and some air (shown in yellow). The long green pipe goes down into the water and then out of the jar. To start the water flowing, you first need to get the green pipe working like a regular siphon. This means filling the pipe with water so it starts to pull water out of the jar.

Balancing the Pressure

As water flows out through the green pipe, the amount of water inside the jar goes down. This would normally cause the air pressure inside the jar to drop. But here's where the orange pipe comes in! Because the pressure inside the jar tries to become lower than the air pressure outside, air gets sucked in through the orange pipe. The end of this orange pipe is usually placed just below the water level.

Constant Flow Secret

The air entering through the orange pipe keeps the air pressure inside the jar the same as the outside air pressure at the level of the orange pipe's opening. This clever balance means that the water is always pushed out of the green pipe with the same force. That's why the water flows out at a steady speed and amount, from start to finish! It's all about keeping the pressure balanced.

Images for kids

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  Mariotte's bottle