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Here's a Hyman flash tube, I think one of my favourite physics toys I've come across.
It shows a wonderful demonstration of the gas law, what's called Charles' Law;
as pressure increases temperature increases, as I know from when
I'm pumping up a bicycle tyre.
So this is an extreme version of a bicycle pump really.
Here's some fuel, which is just a little bit of cotton wool,
and then we put a clear plastic tube on top,
and this plunger that's got a nice grommet on it,
is going to plunge down and heat up the air inside
very, very rapidly so the temperature in here increases
up to the flash point of the cotton wool.
And it will set fire to it.
I need to stand to put a bit of beef in it.
So, here we go.
Ready with the plunge, 5, 4, 3, 2, 1.
[Plunges and sets fire to cotton wool]
Wow, it lit up immediately.
That's a bit of magic [blows in tube], a bit easier than rubbing it with a stick
like primitive man did.
Now if we put a little bit of flash paper in it, which they sell to me in magic studios,
this goes instantly in a lovely bright yellow flame.
This will do the same thing. Here we go again...
Instant catching fire, 5, 4, 3, 2, 1.
[Plunges and sets fire to flash paper]
Oh, it worked.