Smoke Ring Machine

What to do:

Take a tin of tomatoes or beans and eat the contents (or just keep them for later if you aren’t hungry!). Remove the top and bottom of the can completely, so you have an empty metal tube. Use some sandpaper to smooth down any sharp bits of metal. Or, you can use an empty toilet roll if you like.

Take an old CD (it’s all about mp3’s now anyway!) and tape or glue it to one end, so the hole is in the centre. Now, cut the neck off a balloon and stretch the round part of it across the other end of the tin or tube.

Now you need to find some way to fill it with smoke or mist you can see. We used a smoke machine on the show which you can buy from toy shops or electronics shops such as Maplins. We wouldn’t recommend using cigarette smoke for health reasons.

With a gently pat to the balloon end of the tin, tiny little smoke rings will emerge from the other end! With some practice you can use the air from the machine to blow out a candle.

How does this work?

As the air is pushed out of the tube, it gets slowed down at the edges of the hole in the CD. The faster moving air in the centre is at a lower pressure and this holds the ‘doughnut’ of moving air together creating a ring that moves through the air. The proper name for this shape is a ‘torus’.

So what?

A smoke ring is a kind of vortex, and vortices are seen all over the place, from the water going down your plughole to huge tornadoes. Using smoke just makes the air movement visible which helps us understand what is going on. Understanding air movement and vortices can help us to predict weather systems and storms.

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