How does a petrol pump nozzle know when to stop

A. The nozzle contains a small pipe that constantly sucks air from the end because it’s connected to a vacuum at the end of the hose.

When your petrol tank is full, and the nozzle is actually sitting in petrol rather than air, the pipe will suck this petrol through the pipe, rather than air, causing a drop in pressure that is detected by a valve, which shuts off the petrol supply.

Q. Where does petrol come from

A. Petrol, along with many other products is manufactured from crude oil. Crude oil, which can be anything from a yellow, red, green or black liquid, started being created around 400 million years ago. It was formed from the dead bodies of plants and animals in the sea.

The bodies sank to the ocean floors and gradually became covered with mud. Eventually the pressure and heat from the Earth’s processes compressed the bodies, forming crude oil.

Q. How does crude oil become the refined petrol that powers our cars

A. Via oil refineries that break the crude down into its constituent parts. The oil is separated in a distilling tower using the different boiling parts of each part, or fraction. The lightest part rises to the top and evaporates, condensing into liquids on contact with collecting trays and so on until all the various fractions have been separated.

Even so, most of the products need to be refined further into useable products. These conversion processes use chemicals to break down and change the fractions to make new refined products. The final stage in the refining process is called blending and normal involves adding chemicals that improve or change the products.

For example chemicals are added to make petrol useable in engines and antioxidants are needed to allow it to be stored for long periods of time.

Do you have a question about a source of power Click here to ask.

by Lisa Cardy