WEBVTT Kind: captions Language: en-US 00:00:00.080 --> 00:00:05.340 I don’t know about you, but I find cooking rice to be an extremely difficult task. 00:00:05.340 --> 00:00:07.740 Luckily somebody invented the automatic rice cooker 00:00:07.740 --> 00:00:10.300 and now all of my rice cooking problems have been solved! 00:00:10.300 --> 00:00:11.300 Hooray! 00:00:11.300 --> 00:00:15.280 Now, you might think that rice cookers are a pretty boring small kitchen appliance. 00:00:15.280 --> 00:00:17.600 But actually, they’re among the... 00:00:17.600 --> 00:00:18.560 well, OK... 00:00:18.560 --> 00:00:21.360 If we’re looking at what they *do* then yeah, heh 00:00:21.360 --> 00:00:23.180 this ain’t no toaster, that’s for sure! 00:00:23.180 --> 00:00:26.580 But, while the device itself may seem pretty unremarkable, 00:00:26.580 --> 00:00:28.100 and indeed is, 00:00:28.100 --> 00:00:31.020 the principle by which it works is fascinating! 00:00:31.020 --> 00:00:34.380 Simply by exploiting one of the chemical properties of water, 00:00:34.380 --> 00:00:38.260 this device can tell when the rice has been cooked, and the result is a 00:00:38.260 --> 00:00:42.020 perfectly cooked batch of the world’s second favorite grain. 00:00:42.020 --> 00:00:45.350 Assuming you got the water to rice ratio correct, that is. 00:00:45.350 --> 00:00:46.820 So how does it work? 00:00:46.820 --> 00:00:50.360 Well, to find out, first we need to learn a little bit about water. 00:00:50.360 --> 00:00:55.440 As I’m sure we all know, at sea level water boils at 212 degrees Fahrenheit. 00:00:55.440 --> 00:00:57.820 Isn’t that just a delightfully easy number to remember? 00:00:57.820 --> 00:01:01.420 I don’t know what the heck that is in Celsius, probably some silly arbitrary thing, 00:01:01.420 --> 00:01:03.960 but anyway that number isn’t the whole story. 00:01:03.960 --> 00:01:07.060 You see, water doesn’t just boil at that temperature. 00:01:07.060 --> 00:01:08.560 It *starts* to boil. 00:01:08.560 --> 00:01:11.260 See, if you got a pot of water on the stove, and 00:01:11.260 --> 00:01:13.980 you watch its temperature rise with a thermometer, 00:01:13.980 --> 00:01:17.840 well what do you suppose happens once it gets to boiling point? 00:01:17.840 --> 00:01:20.980 You can see the temperature steadily rising as it approaches, 00:01:20.980 --> 00:01:24.400 so you might think that once it hits boiling point the water will just 00:01:24.400 --> 00:01:24.900 *poof* 00:01:24.900 --> 00:01:28.040 disappear and turn into a big 'ol cloud of water vapor. 00:01:28.040 --> 00:01:30.300 But of course, that’s not what happens. 00:01:30.300 --> 00:01:34.320 The temperature just plateaus, and it won’t go any higher. 00:01:34.320 --> 00:01:35.730 But the stove 00:01:35.730 --> 00:01:37.040 (or hot plate) 00:01:37.040 --> 00:01:42.140 is still dumping energy into the water, so why isn’t it getting any hotter? 00:01:42.140 --> 00:01:47.890 The answer is physics, and more specifically the principle known as the latent heat of vaporization. 00:01:47.890 --> 00:01:53.040 This is a fun concept important to many fields of study, from meteorology to refrigeration. 00:01:53.040 --> 00:01:57.450 Also known as enthalpy of vaporization, this is the amount of energy required to transition 00:01:57.450 --> 00:01:59.180 a liquid into a gas. 00:01:59.180 --> 00:02:03.860 And it’s a LOT more energy than just raising the temperature of that liquid 00:02:03.920 --> 00:02:05.900 (boiling of water starts to becomes audible) OK, what we need to understand here is how 00:02:05.900 --> 00:02:08.500 latent heat differs from sensible heat. 00:02:08.500 --> 00:02:11.620 Sensible heat is something like, oh I dunno 68 degrees? 00:02:11.620 --> 00:02:13.280 That's a a pretty sensible room temperature-- 00:02:13.280 --> 00:02:15.430 Ohhh, oh, Sensible, 00:02:15.430 --> 00:02:17.640 like can be sensed. Got it. (though it is still spelled "sensible") 00:02:17.640 --> 00:02:20.660 Sensible heat is the figure we can sense, or measure. 00:02:20.660 --> 00:02:24.420 The thermometer is looking at the sensible heat when it tells us how hot something is. 00:02:24.420 --> 00:02:29.670 But as the water (or any other substance) reaches its phase change temperature, adding energy 00:02:29.670 --> 00:02:32.340 into it will not raise the sensible heat. 00:02:32.340 --> 00:02:34.740 Instead, that energy gets absorbed by the 00:02:34.740 --> 00:02:39.590 molecules to free them from their liquid state, and that takes a heckuva lotta energy. 00:02:39.590 --> 00:02:41.060 (boiling gets louder) We don’t need to be too worried about that 00:02:41.060 --> 00:02:42.520 extra energy right now. 00:02:42.520 --> 00:02:45.720 We’ll get to that when we tackle air conditioning and refrigeration. 00:02:45.720 --> 00:02:48.660 But what you need to know for the purposes of cooking rice 00:02:48.660 --> 00:02:53.640 is that liquid water cannot exist at a temperature higher than its boiling point. 00:02:53.640 --> 00:02:57.760 Dumping more energy into it will simply make it boil away faster. 00:02:57.760 --> 00:03:00.790 It will not make it get any hotter. 00:03:00.790 --> 00:03:04.680 So what does that have to do with cooking rice? Well, see, cooking rice is all about 00:03:04.680 --> 00:03:09.360 making water hot so that the rice will absorb it and the starches convert to the other... 00:03:09.360 --> 00:03:10.940 things and all that jazz. 00:03:10.940 --> 00:03:14.300 And that rice is cooked once it has absorbed all the water. 00:03:14.300 --> 00:03:18.430 You don’t want to keep cooking it after that point or it will burn, and you don’t want to not 00:03:18.430 --> 00:03:22.970 cook it long enough or you’ll have rice al dente which I’m pretty sure isn’t actually a thing. 00:03:22.970 --> 00:03:28.400 So, in an ideal world, we’d have a way to tell precisely when that rice has finished cooking. 00:03:28.400 --> 00:03:32.160 And, thanks to latent heat of vaporization, we do! 00:03:32.160 --> 00:03:35.320 See, water can’t get hotter than its boiling point. 00:03:35.320 --> 00:03:37.860 But cooked rice can. 00:03:37.860 --> 00:03:41.500 And once you know that little factoid, you can easily make a device which will cook rice 00:03:41.500 --> 00:03:43.960 to completion, and automatically stop. 00:03:43.960 --> 00:03:46.800 This is a very basic rice cooker. 00:03:46.800 --> 00:03:48.100 It cooks rice... 00:03:48.100 --> 00:03:49.280 and that’s it. 00:03:49.280 --> 00:03:51.589 None of that fancy multi-function nonsense. 00:03:51.589 --> 00:03:52.180 Side-note - 00:03:52.180 --> 00:03:56.069 I actually have a nicer rice cooker with a whole electronic interface 00:03:56.069 --> 00:04:01.250 thing that can do fancy things like slow cook or steam vegetables but it’s got one of 00:04:01.250 --> 00:04:05.820 those gasket deals going on in the lid and frankly it gets really gross all the time. 00:04:05.820 --> 00:04:07.420 And it’s a pain to clean. 00:04:07.420 --> 00:04:10.761 Now I’m not certainly someone who eats rice as a staple food but when I 00:04:10.761 --> 00:04:15.920 discovered that this cheap, basic unit had just a plain glass lid and both it and the 00:04:15.920 --> 00:04:20.900 bowl are dishwasher safe, I was like “Life Changer!” and bought it on the spot. 00:04:20.900 --> 00:04:26.600 Truthfully I prefer it to my fancier one by a large margin simply because it doesn’t get gross and it cooks 00:04:26.600 --> 00:04:30.080 rice just as well, which is all I use a rice cooker for anyway. 00:04:30.080 --> 00:04:34.540 Plus it doesn’t beep incessantly for 15 seconds when it’s done, so that’s a nice plus. 00:04:34.540 --> 00:04:39.960 Sometimes basic is in fact better, but that’s all down to your personal priorities and preferences, 00:04:39.960 --> 00:04:43.900 and I’m sure you all tell me why my priorities and preferences are wrong! 00:04:43.900 --> 00:04:49.320 Anyway, this device is so incredibly simple and yet entirely automatic and I just love that sort of thing. 00:04:49.320 --> 00:04:52.110 At the bottom, you’ve got a round heating element with a little 00:04:52.110 --> 00:04:54.340 button thing poking up through the center. 00:04:54.340 --> 00:04:58.440 This guy is spring-loaded and is the heart of its automatic operation. 00:04:58.440 --> 00:05:02.200 The rice cooker has two modes: Cooking, and keep warm. 00:05:02.200 --> 00:05:05.219 Whenever it’s plugged in it’s in the warming mode. 00:05:05.219 --> 00:05:09.870 If we flip it over and take off the bottom, we’ll see that there’s a buncha wires. 00:05:09.870 --> 00:05:14.189 In the keep-warm state, current comes in through the power cord, and passes through this big 00:05:14.189 --> 00:05:18.389 resistor to limit the current before going through the heating element. The lever to 00:05:18.389 --> 00:05:24.669 engage cooking is attached to that button thing, and importantly it closes these contacts. 00:05:24.669 --> 00:05:28.900 This bypasses the resistor and allows the heating element to run at full power. 00:05:28.900 --> 00:05:31.020 In this case, it’s a mere 300 watts. 00:05:31.020 --> 00:05:33.580 This is after all a tiny little rice cooker. 00:05:33.580 --> 00:05:37.020 Also, this changes which of the little neon indicators lights up. 00:05:37.020 --> 00:05:38.200 Useful! 00:05:38.200 --> 00:05:41.160 You’ll see that right now I cannot get the lever to stay engaged. 00:05:41.160 --> 00:05:43.440 That’s because the button thing isn’t depressed. 00:05:43.440 --> 00:05:46.000 This serves as a safety feature to prevent the heating element 00:05:46.000 --> 00:05:49.480 from operating at full power if the pot were to be removed. 00:05:49.480 --> 00:05:52.100 Ordinarily the weight of the bowl would press down on it, 00:05:52.100 --> 00:05:54.900 but in this case I need to substitute my fingers. 00:05:54.900 --> 00:05:58.960 With it depressed, you’ll see that the lever will now stick in the down position. 00:05:58.960 --> 00:06:03.360 What’s keeping it there is a permanent magnet, which you can just barely see here. 00:06:03.360 --> 00:06:05.720 And this is where things get really interesting. 00:06:05.720 --> 00:06:08.979 The magnet is sticking to the bottom of the button, 00:06:08.980 --> 00:06:13.060 and it’s overcoming the force of a second spring inside the button trying to push it away. 00:06:13.060 --> 00:06:15.400 Which, luckily, it manages to do. 00:06:15.400 --> 00:06:17.140 But here’s the thing about magnets. 00:06:17.140 --> 00:06:20.780 Get things hot, and suddenly magnets don’t work anymore. 00:06:20.780 --> 00:06:23.580 Uh-oh here comes a Blanket Statement Abatement Alert! 00:06:23.580 --> 00:06:25.700 Magnets are confusing. 00:06:25.700 --> 00:06:26.729 Ferromagnetism. 00:06:26.729 --> 00:06:27.760 Paramagnetism. 00:06:27.760 --> 00:06:28.800 Curie points. 00:06:28.800 --> 00:06:30.800 There’s just so much that hurts my brain. 00:06:30.800 --> 00:06:34.500 So, please do not assume I’m an expert here, ‘cause I’m not. 00:06:34.500 --> 00:06:37.680 Regarding this magnetic phenomenon I’m about to describe, 00:06:37.680 --> 00:06:40.740 this is my very best interpretation from what I’ve uncovered through looking 00:06:40.740 --> 00:06:45.330 at patents, a very rudimentary understanding of magnetic interaction, and also some forum 00:06:45.330 --> 00:06:47.560 threads where people were arguing about this. 00:06:47.560 --> 00:06:50.860 If I’ve gotten something wrong here, please correct me in the comments. 00:06:50.860 --> 00:06:54.940 And also, please check to see if someone else has already provided a correction, 00:06:54.940 --> 00:06:55.820 thanks. 00:06:55.820 --> 00:07:00.260 All magnetic materials have what’s called a Curie temperature, or Curie point. 00:07:00.260 --> 00:07:06.520 For ordinary ferromagnetic materials, once you reach this temperature they cease to be ferromagnetic at all. 00:07:06.520 --> 00:07:10.440 In the case of a permanent magnet, if you get it to the Curie temperature ... 00:07:10.440 --> 00:07:13.100 you’ve broken the magnet permanently. 00:07:13.100 --> 00:07:15.480 So now it’s a permanent not-magnet. 00:07:15.480 --> 00:07:18.440 But materials that are attracted to permanent magnets 00:07:18.440 --> 00:07:21.780 will regain their attraction once they’ve cooled back down. 00:07:21.780 --> 00:07:26.200 This button thing is made of an alloy that has a Curie temperature just a bit higher 00:07:26.210 --> 00:07:28.240 than the boiling point of water. 00:07:28.240 --> 00:07:31.840 This allows it to function as a temperature-dependent kill switch. 00:07:31.840 --> 00:07:36.740 Thanks to the outer spring, it’s always held firmly in contact with the bottom of the pot, 00:07:36.740 --> 00:07:40.160 which ensures it and the pot are at nearly equal temperatures. 00:07:40.160 --> 00:07:46.640 So long as there’s liquid water sitting in that pot, the pot itself cannot get hotter than water's boiling point. 00:07:46.640 --> 00:07:50.900 This means that the button remains magnetic, and the magnet is able to overcome 00:07:50.909 --> 00:07:54.659 the force of the inner spring, so the device stays in cook mode 00:07:54.659 --> 00:07:57.180 But, once the rice has absorbed all of the water 00:07:57.180 --> 00:07:59.960 (and / or once all the remaining water has boiled away) 00:07:59.960 --> 00:08:06.160 the energy being added to the pot by the heating element is no longer being absorbed as latent heat. 00:08:06.160 --> 00:08:10.140 Now, the pot can quickly start to exceed the boiling point of water. 00:08:10.140 --> 00:08:13.160 And once it gets past the Curie point of that little sensing button, 00:08:13.160 --> 00:08:18.260 the magnet is no longer attracted to it, so the spring overcomes the magnet and... 00:08:18.260 --> 00:08:21.520 *click* the rice cooker switches back to the warming mode. 00:08:21.520 --> 00:08:25.309 Now, I don’t know about you, but I think this is some of the most amazing ingenuity 00:08:25.309 --> 00:08:26.300 out there. 00:08:26.300 --> 00:08:32.190 This incredibly basic device is not only exploting the physical properties of water, 00:08:32.190 --> 00:08:37.400 but also the physical properties of magnetism to automate the cooking of rice in an elegant 00:08:37.400 --> 00:08:39.300 and effective way. 00:08:39.300 --> 00:08:43.280 Sure, my fancier rice cooker may have some fuzzy logic and a microcontroller 00:08:43.280 --> 00:08:47.200 in there, but anybody can program an Arduino with some inputs and outputs. 00:08:47.200 --> 00:08:50.560 So this is much more interesting, at least I think so. 00:08:50.560 --> 00:08:55.000 These days, only the most basic rice cookers continue to use this method of automation. 00:08:55.000 --> 00:08:58.900 But, for decades this is just how rice cookers worked. 00:08:58.900 --> 00:09:02.760 I’ve tried to find when exactly this method was first put into production, 00:09:02.760 --> 00:09:07.260 and short of looking through every rice cooker related patent out there, 00:09:07.260 --> 00:09:08.720 the answer isn’t obvious. 00:09:08.720 --> 00:09:13.680 However, it’s been in use at least since the late seventies, having come across this patent. 00:09:13.680 --> 00:09:17.760 And you might be surprised to learn that rice cookers are a rather recent invention. 00:09:17.760 --> 00:09:21.740 When you consider that we’ve had mechanical refrigeration for over a century now, 00:09:21.740 --> 00:09:27.060 it can seem a little weird that it took until 1956 for the first automated rice cooker to appear on sale in 00:09:27.060 --> 00:09:29.220 Japan, produced by Toshiba. 00:09:29.220 --> 00:09:33.760 Those early rice cookers used a sort of double boiler to indirectly heat the pot. 00:09:33.760 --> 00:09:36.610 Everyone’s favorite source of knowledge claims that that went out of style 00:09:36.610 --> 00:09:39.420 in the 1960’s but, citation needed. 00:09:39.420 --> 00:09:40.980 Anyway. That’s it! 00:09:40.980 --> 00:09:42.460 I hope you enjoyed this video. 00:09:42.460 --> 00:09:46.500 While I wouldn’t necessarily call this device Automatic Beyond Belief! 00:09:46.500 --> 00:09:50.060 it is certainly among the most clever forms of automation out there. 00:09:50.060 --> 00:09:52.480 Even if I have to push the lever down. 00:09:52.480 --> 00:09:55.520 And of course, thanks to everyone supporting the channel on Patreon, 00:09:55.520 --> 00:09:58.940 with a special thanks going to these nifty people scrolling up your screen. 00:09:58.940 --> 00:10:02.600 CED part 5 is coming soon, so be on the lookout for it! 00:10:02.600 --> 00:10:04.220 For now, though... 00:10:04.220 --> 00:10:05.120 eat up! 00:10:06.080 --> 00:10:08.940 ♫ insensibly smooth jazz ♫ 00:10:11.510 --> 00:10:13.900 I don’t know about you, but I find … 00:10:13.900 --> 00:10:16.740 the teleprompter to be a little finicky today 00:10:16.740 --> 00:10:18.380 Their among… well ok, 00:10:18.380 --> 00:10:19.500 if we’re looking at they d .. 00:10:19.500 --> 00:10:20.750 yeah no I don’t like THAT take 00:10:20.750 --> 00:10:22.240 So, in an ideal world, 00:10:22.240 --> 00:10:23.680 ( makes weird noises as he checks his shirt ) 00:10:23.680 --> 00:10:25.140 So, in an ideal world… 00:10:25.140 --> 00:10:27.680 It cooks rice. And that’s it. 00:10:27.680 --> 00:10:29.460 None of this … pbbbbttptt 00:10:30.040 --> 00:10:32.060 But, once the rice has absorbed .. bleuw 00:10:32.820 --> 00:10:34.920 I just noticed an error. 00:10:34.920 --> 00:10:35.840 We’ll try to fix it 00:10:35.840 --> 00:10:37.840 Materials that are attracted to permanent 00:10:37.840 --> 00:10:39.360 magnets will regain … 00:10:39.360 --> 00:10:41.180 pbbpbpbppb (this one was excessive) 00:10:41.920 --> 00:10:44.240 Hey, it's me! The SPIRIT OF THE CREDITS! 00:10:45.080 --> 00:10:48.480 Usually, I'm the SPIRIT OF THE ENDSCREEN but the shoot went real well and there aren't many bloopers. 00:10:48.820 --> 00:10:51.160 So now you get to spend more time with ME!!! 00:10:51.360 --> 00:10:54.000 And I'm here to tell you that you're a pretty cool human! 00:10:54.000 --> 00:10:57.300 Well, and I suppose there could be some non-humans watching, too. You're all cool! 00:10:58.400 --> 00:11:02.040 Oh, wait, but y'all need to be able to read to see this part. 00:11:02.520 --> 00:11:06.520 Does that mean the SPIRIT OF THE ENDSCREEN can't talk to animals? 00:11:06.940 --> 00:11:09.180 Goodness isn't this an existential crisis? 00:11:09.500 --> 00:11:10.440 And so is reaching the end! 00:11:10.440 --> 00:11:10.940 AUGH!!