[MUSIC PLAYING]
Hey, there.
I'm Josh Clark.
This is Brain Stuff.
Have you ever been
pumping gas in your car,
and all of a sudden, pssh, it
just shuts off in your hand.
Bam.
Maybe it takes a finger off.
That kind of thing.
How does the gas nozzle
know when to shut off?
Well, I'm here to explain.
It's actually
surprisingly complicated.
You ever heard of
the Venturi effect?
If you take a tube and you pitch
it in the middle, then fluid--
and remember, fluid can be gas.
It can be liquid.
It doesn't just have to
be water or something.
After the pinch, after it
goes through the pinch,
it becomes compressed.
And as its velocity
speeds up, the pressure
on the other side of the
tube actually decreases.
Keep that in mind.
That's the Venturi Effect.
If you look at a
gas nozzle, you'll
see a little hole
toward the end.
And that hole actually
leads to a tube.
And that tube runs all
the way up the length
of the gas nozzle.
And it usually tees off.
On one side, you've
got a Venturi tube.
On the other side,
you've got a tube
leading to a diaphragm of air.
Now that diaphragm of air is
all blown up nice and big,
while there's air running
through the nozzle sensor.
So while you're pumping
gas, and gas is in the tank,
and you're still
filling it up, air
is moving through this little
sensor pipe quite nicely.
The pressure on one end
of the Venturi tube,
which is on this
side, is nice and low.
And on the other
side, the diaphragm
is nice and puffed up.
Air pressure, no problem.
But as the gas starts to
rise, maybe it starts to foam,
or it starts to just
simply fill up the tank.
That sensor, that pipe,
starts to suck up gas.
And when the gas is sucked
up, the density of gas
is a lot heavier than
the density of just air.
The Venturi tube all of a
sudden changes in pressure,
which creates suction on
the other end of this pipe,
which sucks the diaphragm,
which collapses a little bit,
triggering an
automatic shut off.
Seriously, that's what's
going on in your gas nozzle
when you're pumping
gas and it fills up.
That's how it knows
your tank is full.
So I guess maybe
ruminate on this.
Chew on it.
Think about it for possibly
the rest of your life.
It is really complex,
but pretty cool.
It's not magic, I guess
is what I'm trying to say.
I'm sure you like this video.
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