December 24, 2025 • 10 mins
These small appliances help home cooks achieve excellent rice via two categories of technology: ingeniously simple physics, or incredibly complex algorithms. Learn about heat-sensitive switches and fuzzy logic in this episode of BrainStuff, based on this article: https://home.howstuffworks.com/rice-cooker.htm/printable For more about the history of rice cookers, check out this episode of Lauren's other podcast, Savor: The Warm and Fuzzy Rice Cooker Episode
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Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Speaker 1 (00:01):
Welcome to Brainstuff, a production of iHeartRadio, Hey Brainstuff, Lauren Bolebaum. Here,
Burned chunks or gooey paste can be the disappointing result
of rice gone wrong, but with the use of a
rice cooker, the odds even up for even the glutsiest
in the kitchen. A rice is the staple grain in
(00:25):
many cuisines around the world. But before the invention and
adoption of modern kitchen technology alike electric and gas heating elements,
cooking rice was a finicky, hours long process that required
you to stand around over a cast iron pot, making
adjustments to a coal or wood fire in order to
get the heat just right during different parts of the
(00:46):
cooking process. Although simple electric rice cookers go back to
the nineteen twenties in Japan, the first commercial one for
home use didn't debut until nineteen fifty six from Tashiba. People,
and perhaps specifically women who often took on the task
were Ready. Company records show that just four years later,
(01:08):
about half of Japanese homes had a rice cooker. These days,
rice cookers range from basic models that'll run you less
than thirty bucks to ones with fancy features that cost
over five hundred and Although they're ostensibly meant for cooking
you know, rice, they can be very versatile. Some people
use rice cookers as their primary cooking tool for everything
(01:31):
from spaghetti to spare ribs to scrambled eggs. So today
let's talk about the technologies behind rice cookers. Rice needs
two things to go from hard, shelf stable grains to
tender morsels, lots of water and lots of heat. You
generally accomplish this by boiling grains of dried rice in
(01:53):
water anywhere from equal parts of each to twice as
much water by volume. The rice is done when all
of the water has been absorbed and or steamed off,
and the grains are whatever degree of tender you're looking for.
It is ideal if you can do this without melting
a layer of rice into a sticky, burnt mass at
(02:14):
the bottom of the pot. There are a few ways
to accomplish this automatically. Most start with an electric heating
element set into a base which can also hold a
cooking pot. You add rice and water and cover with
the lid that came with the appliance. The heating element
heats the pot, which boils the water. But how does
(02:34):
it know when it's done. The classic technology, the least expensive.
The type I've got operates on a simple heat sensitive
magnetized switch. Okay, you turn on this type of rice
cooker by pressing down a switch on the outside of
the unit, and when you do, you'll hear a little clock.
That's because the switch is connected to a lever that
(02:56):
brings two surfaces in contact with each other that are
electrically conducive. This completes an electrical circuit and powers the
heating element. The circuit stays closed because the two surfaces
are magnetic, but one surface, the upper surface of the pair,
is made of a material that's only magnetic up to
about one hundred and two degrees celsius, which is right
(03:19):
above the boiling point of water. This is a very
clever bit of physics. Water boils at one hundred degrees
celsius and won't get hotter than that at normal Earth pressure.
So as long as there's water in the pot as
the rice is cooking, the temperature at the bottom of
the pot will hold steady. At one hundred the temperature
(03:41):
is in check thanks to the presence of water, but
when it's all absorbed and or boiled off, the heating
element can get to work on the pot and or
the rice itself, which can get considerably hotter than one
hundred degrees at normal Earth pressure, so the temperature at
the bottom of the pan leaps up, at which point
(04:01):
our temperature sensitive magnet stops being magnetic and drops the
other half of the pair, breaking the circuit and turning
the heating element off with another little clunk. Except in
a lot of rice cookers like this, the heating element
doesn't turn all the way off, but rather switches to
a warming function. This works thanks to another type of
(04:23):
heat sensitive switch called a bimetal switch. A bimetal switch
is a type of switch that's made up of two
types of metals sandwiched together. Makes sense, right. Each of
the two is chosen because they are bendable and because
they expand at different rates when exposed to heat. So
the switch starts out flat but will bend one way
(04:44):
or the other at different temperatures because the metals are
expanding or shrinking at different rates, and you can use
this property to connect and disconnect a circuit at different temperatures.
In the case of our rice cooker, at around sixty
degrees ce elius, that's one forty fahrenheit fairly cool. The
switch bends and connects the circuit, turning the heating element
(05:06):
on a butt at around eighty celsius or one hundred
and seventy five fahrenheit fairly hot. The switch bends the
other way, breaking the circuit and turning the element off.
It will keep toggling, holding the temperature of the pot
nice and warm until you unplug the unit. But of
(05:26):
course we humans are not confined to manual physical switches anymore.
Digital rice cookers contain digital thermometers connected to a simple
computer that can be programmed at the touch of a
few buttons on the outside of the unit to heat
or warm the pot, two particular temperature settings, four particular
lengths of time, like the way that we use standard microwaves.
(05:48):
Computer controlled rice cookers were first introduced in nineteen seventy nine.
But if you are going to go ahead and put
a computer into a rice cooker, why not ask it
to do a bit more work for you. Rice cookers
were one of the first home appliances to make use
of the theory of fuzzy logic, which was developed by
computer scientists in the nineteen seventies and now helps everything
(06:11):
from washing machines to refrigerators to subway cars function. Fuzzy
logic is sort of what it sounds like, logic with variables.
Digital devices operate on boolean logic, which means ones in
zeros you know on or off, yes or no. Fuzzy
logic opens up the field of answers to all of
(06:33):
the numbers in between one and zero. Devices programmed with
it can recognize an almost yes versus a slightly yes
and act accordingly. This lets you program algorithms that take
variables into consideration, like not just is the pot hot,
but is it getting hotter quickly, and then make a
(06:55):
decision about how to control the temperature based on that.
Idea is that these machines can adjust for the actual
circumstances occurring in real time. Maybe the ambient pressure is
making the cooking go faster, or you added too much water,
and it can cook the rice perfectly regardless. It's way
(07:15):
better than just using on off temperature settings, and probably
better than any adjustments a hungry and impatient human might make.
While fuzzy logic rice cookers function under the same premise
as basic models, their mathematical programming can deliver a slew
of customized cooking options, making precise fluctuations in cooking time
(07:35):
and temperature depending on the programs selected. These may include
settings for white rice of varying textures, sushi rice, jasmine rice,
brown rice, germinated brown rice, mixed rices, knge steel cutoats,
rapid cooking, extended warming, and reheating. And that's just the beginning.
(07:56):
Some machines have settings for steaming foods, baking cakes, auto cleaning,
and delayed timers, so you can preset the machine to
start cooking at a particular time. Oh and if you
do want a layer of crisp, golden brown rice at
the bottom of your pot for dishes like tadig, there
are rice cookers for that too. You add a bit
(08:17):
of vegetable oil to the pot, and after the main
cooking is done, a timer holds the pot to the
heat long enough to crispit. There are also rice cookers
out there that don't use a standard electric heating element.
These days, you can find models that use induction heating technology,
which I could have sworn had already done an episode about,
but I have not, and I'll have to rectify that
(08:38):
in the future. Very basically, induction cookers don't waste energy
heating an element that then heats a pan, but rather
use magnetic fields to heat the pan directly. There are
also pressure rice cookers, which seal and pressurize their contents
to allow for faster cooking times and hotter temperatures. Pressure
cooking also a whole different episode. Whatever kind of rice
(09:02):
cooker you're using, there are all kinds of recipes out
there for how to get the most out of it.
When it comes to rice and beyond, at a certain point,
it's a hot pad with a fitted pot. Anything you
want to warm or cook, especially anything involving a lot
of liquid, can be done in a rice cooker with
enough tenacity a rice cooker. Poached fruit, hard boiled eggs,
(09:23):
homemade soups, whatever you're cooking in it. Take a moment
to appreciate your humble or not so humble rice cooker,
and if you don't have one, consider picking up a
basic model. After all, it's a robot that, if it
could want things, would want you to eat good rice.
That's a good robot to have around. Today's episode is
(09:49):
based on the article how rice cookers work on HowStuffWorks
dot com, written by Jessica Tooothman for more about the
history of rice cookers. Check out my other podcast Savor
for the Warm and Fuzzy rice Cooker episode. Brainstuff is
production by Heart Radio in partnership with how stuffworks dot
com and is produced by Tyler Klang. But four more
podcasts from iHeartRadio. Visit the iHeartRadio app, Apple Podcasts, or
(10:12):
wherever you listen to your favorite shows.
Welcome to Brainstuff, a production of iHeartRadio, Hey Brainstuff, Lauren Bolebaum. Here,
Burned chunks or gooey paste can be the disappointing result
of rice gone wrong, but with the use of a
rice cooker, the odds even up for even the glutsiest
in the kitchen. A rice is the staple grain in
(00:25):
many cuisines around the world. But before the invention and
adoption of modern kitchen technology alike electric and gas heating elements,
cooking rice was a finicky, hours long process that required
you to stand around over a cast iron pot, making
adjustments to a coal or wood fire in order to
get the heat just right during different parts of the
(00:46):
cooking process. Although simple electric rice cookers go back to
the nineteen twenties in Japan, the first commercial one for
home use didn't debut until nineteen fifty six from Tashiba. People,
and perhaps specifically women who often took on the task
were Ready. Company records show that just four years later,
(01:08):
about half of Japanese homes had a rice cooker. These days,
rice cookers range from basic models that'll run you less
than thirty bucks to ones with fancy features that cost
over five hundred and Although they're ostensibly meant for cooking
you know, rice, they can be very versatile. Some people
use rice cookers as their primary cooking tool for everything
(01:31):
from spaghetti to spare ribs to scrambled eggs. So today
let's talk about the technologies behind rice cookers. Rice needs
two things to go from hard, shelf stable grains to
tender morsels, lots of water and lots of heat. You
generally accomplish this by boiling grains of dried rice in
(01:53):
water anywhere from equal parts of each to twice as
much water by volume. The rice is done when all
of the water has been absorbed and or steamed off,
and the grains are whatever degree of tender you're looking for.
It is ideal if you can do this without melting
a layer of rice into a sticky, burnt mass at
(02:14):
the bottom of the pot. There are a few ways
to accomplish this automatically. Most start with an electric heating
element set into a base which can also hold a
cooking pot. You add rice and water and cover with
the lid that came with the appliance. The heating element
heats the pot, which boils the water. But how does
(02:34):
it know when it's done. The classic technology, the least expensive.
The type I've got operates on a simple heat sensitive
magnetized switch. Okay, you turn on this type of rice
cooker by pressing down a switch on the outside of
the unit, and when you do, you'll hear a little clock.
That's because the switch is connected to a lever that
(02:56):
brings two surfaces in contact with each other that are
electrically conducive. This completes an electrical circuit and powers the
heating element. The circuit stays closed because the two surfaces
are magnetic, but one surface, the upper surface of the pair,
is made of a material that's only magnetic up to
about one hundred and two degrees celsius, which is right
(03:19):
above the boiling point of water. This is a very
clever bit of physics. Water boils at one hundred degrees
celsius and won't get hotter than that at normal Earth pressure.
So as long as there's water in the pot as
the rice is cooking, the temperature at the bottom of
the pot will hold steady. At one hundred the temperature
(03:41):
is in check thanks to the presence of water, but
when it's all absorbed and or boiled off, the heating
element can get to work on the pot and or
the rice itself, which can get considerably hotter than one
hundred degrees at normal Earth pressure, so the temperature at
the bottom of the pan leaps up, at which point
(04:01):
our temperature sensitive magnet stops being magnetic and drops the
other half of the pair, breaking the circuit and turning
the heating element off with another little clunk. Except in
a lot of rice cookers like this, the heating element
doesn't turn all the way off, but rather switches to
a warming function. This works thanks to another type of
(04:23):
heat sensitive switch called a bimetal switch. A bimetal switch
is a type of switch that's made up of two
types of metals sandwiched together. Makes sense, right. Each of
the two is chosen because they are bendable and because
they expand at different rates when exposed to heat. So
the switch starts out flat but will bend one way
(04:44):
or the other at different temperatures because the metals are
expanding or shrinking at different rates, and you can use
this property to connect and disconnect a circuit at different temperatures.
In the case of our rice cooker, at around sixty
degrees ce elius, that's one forty fahrenheit fairly cool. The
switch bends and connects the circuit, turning the heating element
(05:06):
on a butt at around eighty celsius or one hundred
and seventy five fahrenheit fairly hot. The switch bends the
other way, breaking the circuit and turning the element off.
It will keep toggling, holding the temperature of the pot
nice and warm until you unplug the unit. But of
(05:26):
course we humans are not confined to manual physical switches anymore.
Digital rice cookers contain digital thermometers connected to a simple
computer that can be programmed at the touch of a
few buttons on the outside of the unit to heat
or warm the pot, two particular temperature settings, four particular
lengths of time, like the way that we use standard microwaves.
(05:48):
Computer controlled rice cookers were first introduced in nineteen seventy nine.
But if you are going to go ahead and put
a computer into a rice cooker, why not ask it
to do a bit more work for you. Rice cookers
were one of the first home appliances to make use
of the theory of fuzzy logic, which was developed by
computer scientists in the nineteen seventies and now helps everything
(06:11):
from washing machines to refrigerators to subway cars function. Fuzzy
logic is sort of what it sounds like, logic with variables.
Digital devices operate on boolean logic, which means ones in
zeros you know on or off, yes or no. Fuzzy
logic opens up the field of answers to all of
(06:33):
the numbers in between one and zero. Devices programmed with
it can recognize an almost yes versus a slightly yes
and act accordingly. This lets you program algorithms that take
variables into consideration, like not just is the pot hot,
but is it getting hotter quickly, and then make a
(06:55):
decision about how to control the temperature based on that.
Idea is that these machines can adjust for the actual
circumstances occurring in real time. Maybe the ambient pressure is
making the cooking go faster, or you added too much water,
and it can cook the rice perfectly regardless. It's way
(07:15):
better than just using on off temperature settings, and probably
better than any adjustments a hungry and impatient human might make.
While fuzzy logic rice cookers function under the same premise
as basic models, their mathematical programming can deliver a slew
of customized cooking options, making precise fluctuations in cooking time
(07:35):
and temperature depending on the programs selected. These may include
settings for white rice of varying textures, sushi rice, jasmine rice,
brown rice, germinated brown rice, mixed rices, knge steel cutoats,
rapid cooking, extended warming, and reheating. And that's just the beginning.
(07:56):
Some machines have settings for steaming foods, baking cakes, auto cleaning,
and delayed timers, so you can preset the machine to
start cooking at a particular time. Oh and if you
do want a layer of crisp, golden brown rice at
the bottom of your pot for dishes like tadig, there
are rice cookers for that too. You add a bit
(08:17):
of vegetable oil to the pot, and after the main
cooking is done, a timer holds the pot to the
heat long enough to crispit. There are also rice cookers
out there that don't use a standard electric heating element.
These days, you can find models that use induction heating technology,
which I could have sworn had already done an episode about,
but I have not, and I'll have to rectify that
(08:38):
in the future. Very basically, induction cookers don't waste energy
heating an element that then heats a pan, but rather
use magnetic fields to heat the pan directly. There are
also pressure rice cookers, which seal and pressurize their contents
to allow for faster cooking times and hotter temperatures. Pressure
cooking also a whole different episode. Whatever kind of rice
(09:02):
cooker you're using, there are all kinds of recipes out
there for how to get the most out of it.
When it comes to rice and beyond, at a certain point,
it's a hot pad with a fitted pot. Anything you
want to warm or cook, especially anything involving a lot
of liquid, can be done in a rice cooker with
enough tenacity a rice cooker. Poached fruit, hard boiled eggs,
(09:23):
homemade soups, whatever you're cooking in it. Take a moment
to appreciate your humble or not so humble rice cooker,
and if you don't have one, consider picking up a
basic model. After all, it's a robot that, if it
could want things, would want you to eat good rice.
That's a good robot to have around. Today's episode is
(09:49):
based on the article how rice cookers work on HowStuffWorks
dot com, written by Jessica Tooothman for more about the
history of rice cookers. Check out my other podcast Savor
for the Warm and Fuzzy rice Cooker episode. Brainstuff is
production by Heart Radio in partnership with how stuffworks dot
com and is produced by Tyler Klang. But four more
podcasts from iHeartRadio. Visit the iHeartRadio app, Apple Podcasts, or
(10:12):
wherever you listen to your favorite shows.
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