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I don’t know about you, but I find cooking
rice to be an extremely difficult task.

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Luckily somebody invented the automatic rice cooker

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and now all of my rice cooking problems have been solved!

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Hooray!

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Now, you might think that rice cookers are
a pretty boring small kitchen appliance.

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But actually, they’re among the...

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well, OK...

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If we’re looking at what they *do* then yeah, heh

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this ain’t no toaster, that’s for sure!

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But, while the device itself may seem pretty unremarkable,

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and indeed is,

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the principle by which it works is fascinating!

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Simply by exploiting one of the chemical properties
of water,

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this device can tell when the rice has been cooked, and the result is a

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perfectly cooked batch of the world’s second favorite grain.

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Assuming you got the water to rice
ratio correct, that is.

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So how does it work?

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Well, to find out, first we
need to learn a little bit about water.

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As I’m sure we all know, at sea level water
boils at 212 degrees Fahrenheit.

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Isn’t that just a delightfully easy number to remember?

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I don’t know what the heck that is in Celsius, probably some silly arbitrary thing,

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but anyway that
number isn’t the whole story.

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You see, water doesn’t just boil at that temperature.

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It *starts* to boil.

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See, if you got a pot of water on the stove,
and

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you watch its temperature rise with a thermometer,

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well what do you suppose happens once it gets to boiling point?

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You can see the temperature steadily rising as it approaches,

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so you might think that once it hits boiling point the water will just

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*poof*

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disappear and turn into a big 'ol cloud
of water vapor.

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But of course, that’s not what happens.

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The temperature just plateaus,
and it won’t go any higher.

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But the stove

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(or hot plate)

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is still dumping energy into
the water, so why isn’t it getting any hotter?

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The answer is physics, and more specifically
the principle known as the latent heat of vaporization.

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This is a fun concept important to many fields
of study, from meteorology to refrigeration.

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Also known as enthalpy of vaporization, this
is the amount of energy required to transition

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a liquid into a gas.

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And it’s a LOT more
energy than just raising the temperature of that liquid

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(boiling of water starts to becomes audible)
OK, what we need to understand here is how

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latent heat differs from sensible heat.

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Sensible heat is something like, oh I dunno 68 degrees?

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That's a a pretty sensible room temperature--

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Ohhh, oh, Sensible,

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like can be sensed. Got it. 
(though it is still spelled "sensible")

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Sensible heat
is the figure we can sense, or measure.

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The thermometer is looking at the sensible heat
when it tells us how hot something is.

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But as the water (or any other substance) reaches
its phase change temperature, adding energy

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into it will not raise the sensible heat.

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Instead, that energy gets absorbed by the

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molecules to free them from their liquid state,
and that takes a heckuva lotta energy.

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(boiling gets louder)
We don’t need to be too worried about that

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extra energy right now.

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We’ll get to that when we tackle air conditioning and refrigeration.

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But what you need to know for the purposes of cooking rice

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is that liquid water cannot
exist at a temperature higher than its boiling point.

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Dumping more energy into it will simply
make it boil away faster.

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It will not make it get any hotter.

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So what does that have to do with cooking
rice? Well, see, cooking rice is all about

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making water hot so that the rice will absorb
it and the starches convert to the other...

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things and all that jazz.

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And that rice is cooked
once it has absorbed all the water.

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You don’t want to keep cooking it after that point or
it will burn, and you don’t want to not

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cook it long enough or you’ll have rice
al dente which I’m pretty sure isn’t actually a thing.

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So, in an ideal world, we’d have a way to
tell precisely when that rice has finished cooking.

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And, thanks to latent heat of vaporization,
we do!

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See, water can’t get hotter than its boiling point.

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But cooked rice can.

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And once you know that little factoid, you can easily make a device which will cook rice

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to completion, and automatically stop.

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This is a very basic rice cooker.

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It cooks rice...

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and that’s it.

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None of that fancy multi-function nonsense.

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Side-note -

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I actually have a nicer rice cooker with a whole electronic interface

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thing that can do fancy things like slow cook
or steam vegetables but it’s got one of

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those gasket deals going on in the lid and frankly it
gets really gross all the time.

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And it’s a pain to clean.

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Now I’m not certainly someone
who eats rice as a staple food but when I

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discovered that this cheap, basic unit had just a
plain glass lid and both it and the

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bowl are dishwasher safe, I was like “Life Changer!”
and bought it on the spot.

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Truthfully I prefer it to my fancier one by a large margin simply because it doesn’t get gross and it cooks

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rice just as well, which is all I use a rice
cooker for anyway.

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Plus it doesn’t beep incessantly for 15 seconds when it’s done, so that’s a nice plus.

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Sometimes basic is in fact better, but that’s all down to your personal priorities and preferences,

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and I’m sure you all tell me why my priorities
and preferences are wrong!

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Anyway, this device is so incredibly simple and yet entirely automatic and I just love that sort of thing.

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At the bottom, you’ve
got a round heating element with a little

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button thing poking up through the center.

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This guy is spring-loaded and is the heart of its automatic operation.

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The rice cooker has two modes: 
Cooking, and keep warm.

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Whenever it’s plugged in it’s in the warming mode.

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If we flip it over and take off the bottom,
we’ll see that there’s a buncha wires.

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In the keep-warm state, current comes in through
the power cord, and passes through this big

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resistor to limit the current before going
through the heating element. The lever to

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engage cooking is attached to that button
thing, and importantly it closes these contacts.

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This bypasses the resistor and allows the
heating element to run at full power.

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In this case, it’s a mere 300 watts.

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This is after all a tiny little rice cooker.

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Also, this changes which of the little neon indicators lights up.

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Useful!

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You’ll see that right now I cannot get the lever to
stay engaged.

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That’s because the button thing isn’t depressed.

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This serves as a
safety feature to prevent the heating element

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from operating at full power if the pot were
to be removed.

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Ordinarily the weight of the bowl would press down on it,

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but in this case
I need to substitute my fingers.

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With it depressed, you’ll see that the lever will now stick in the down position.

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What’s keeping it there is a permanent magnet,
which you can just barely see here.

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And this is where things get really interesting.

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The magnet is sticking to the bottom of the button,

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and it’s overcoming the force of a second
spring inside the button trying to push it away.

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Which, luckily, it manages to do.

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But here’s the thing about magnets.

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Get things hot, and suddenly magnets don’t work anymore.

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Uh-oh here comes a 
Blanket Statement Abatement Alert!

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Magnets are confusing.

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Ferromagnetism.

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Paramagnetism.

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Curie points.

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There’s just
so much that hurts my brain.

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So, please do not assume I’m an expert here, ‘cause I’m not.

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Regarding this magnetic phenomenon I’m about to describe,

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this is my very best interpretation
from what I’ve uncovered through looking

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at patents, a very rudimentary understanding
of magnetic interaction, and also some forum

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threads where people were arguing about this.

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If I’ve gotten something wrong here, please correct me in the comments.

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And also, please check to see if someone else has already provided a correction,

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thanks.

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All magnetic materials have what’s called
a Curie temperature, or Curie point.

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For ordinary ferromagnetic materials, once you reach this temperature they cease to be ferromagnetic at all.

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In the case of a permanent magnet,
if you get it to the Curie temperature ...

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you’ve broken the magnet permanently.

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So now it’s a permanent not-magnet.

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But materials that are attracted to permanent magnets

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will regain their attraction once they’ve cooled back down.

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This button thing is made of an alloy that
has a Curie temperature just a bit higher

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than the boiling point of water.

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This allows it to function as a temperature-dependent 
 kill switch.

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Thanks to the outer spring, it’s
always held firmly in contact with the bottom of the pot,

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which ensures it and the pot are
at nearly equal temperatures.

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So long as there’s liquid water sitting in that pot, the pot
itself cannot get hotter than water's boiling point.

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This means that the button remains
magnetic, and the magnet is able to overcome

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the force of the inner spring,
 so the device stays in cook mode

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But, once the rice has absorbed all of the
water

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(and / or once all the remaining water has boiled away)

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the energy being added to the pot by the heating element is no longer being absorbed as latent heat.

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Now, the pot can quickly
start to exceed the boiling point of water.

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And once it gets past the Curie point of that
little sensing button,

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the magnet is no longer attracted to it, so the spring overcomes the magnet and...

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*click* 
the rice cooker switches back to the warming mode.

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Now, I don’t know about you, but I think
this is some of the most amazing ingenuity

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out there.

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This incredibly basic device is not only exploting the physical properties of water,

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but also the physical properties of magnetism
to automate the cooking of rice in an elegant

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and effective way.

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Sure, my fancier rice cooker
may have some fuzzy logic and a microcontroller

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in there, but anybody can program an Arduino
with some inputs and outputs.

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So this is much more interesting, at least I think so.

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These days, only the most basic rice cookers
continue to use this method of automation.

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But, for decades this is just how rice cookers
worked.

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I’ve tried to find when exactly this method was first put into production,

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and short of looking through every rice cooker related patent out there,

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the answer isn’t obvious.

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However, it’s been in use at least since the late seventies, having come across this patent.

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And you might be surprised to learn that rice
cookers are a rather recent invention.

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When you consider that we’ve had mechanical refrigeration for over a century now,

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it can seem a little weird that it took until 1956 for the first automated rice cooker to appear on sale in

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Japan, produced by Toshiba.

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Those early rice cookers used a sort of double boiler to indirectly heat the pot.

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Everyone’s favorite source
of knowledge claims that that went out of style

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in the 1960’s but, citation needed.

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Anyway. That’s it!

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I hope you enjoyed this
video.

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While I wouldn’t necessarily call this device 
Automatic Beyond Belief!

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it is certainly among the most clever forms of automation out there.

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Even if I have to push the lever
down.

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And of course, thanks to everyone supporting the channel on Patreon,

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with a special thanks
going to these nifty people scrolling up your screen.

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CED part 5 is coming soon, so be on
the lookout for it!

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For now, though...

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eat up!

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♫ insensibly smooth jazz ♫

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I don’t know about you, but I find …

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the teleprompter to be a little finicky today

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Their among… well ok,

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if we’re looking
at they d ..

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yeah no I don’t like THAT take

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So, in an ideal world,

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( makes weird noises as he checks his shirt )

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So, in an ideal world…

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It cooks rice. And that’s it.

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None of this
… pbbbbttptt

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But, once the rice has absorbed .. bleuw

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I just noticed an error.

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We’ll try to fix it

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Materials that are attracted to permanent

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magnets will regain …

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pbbpbpbppb 
(this one was excessive)

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Hey, it's me! The SPIRIT OF THE CREDITS!

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Usually, I'm the SPIRIT OF THE ENDSCREEN but the shoot went real well and there aren't many bloopers.

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So now you get to spend more time with ME!!!

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And I'm here to tell you that you're a pretty cool human!

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Well, and I suppose there could be some non-humans watching, too. You're all cool!

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Oh, wait, but y'all need to be able to read to see this part.

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00:11:02,520 --> 00:11:06,520
Does that mean the SPIRIT OF THE ENDSCREEN can't talk to animals?

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Goodness isn't this an existential crisis?

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And so is reaching the end!

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AUGH!!