I mix up a bit of the terminology and ideas I think. But feel the results of the experiment still stand. If you have any other info you'd like to correct me on for the next one, please a comment.
So at high frequencies in telecommunications we often talk about forwarded power and reflected power. If there is a mismatch in the route of the rf signal, it reflexts power back to the transmitter, which can damge it. In the case of the microwave, the magnetron is the transmitter and if there is nothing in the microwave, power reflects back to the magnetron, so it heats up. As the magnetron is considered a vacuum tube and not silicon based electrical part, maybe as it heats up, it does not draw more power. Usually silicon based parts like transistors are the "more power more heat" type of devices, cause their resistance decreases with heat. This experiment could be more precise, if you locate a temperature sensor on the magnetron itself and measure the temp while running it empty or full. Cool video btw, nicely cut!
@@zozozoli I believe there are 2 different thermal fuses on it for some reason. There's one that shuts off the whole thing, and another that shuts off just the magnetron. The one that shuts off the whole thing trips first usually. I did notice that the first time I ran it for this experiment the drew the most current, despite being empty. Every subsequent run it drew the more stable currents. If it truly draws less when it's hotter, then I think that may be the reason. I don't think I have a fast or precise enough thermometer to capture the temperature well enough. I plan on remaking with video with all that I've learned from you guys' helpful comments.
@@FreedomOfDegree maybe the second fuse breaks permanently, so if your magnetron gets damaged and heats up way more than it should, it disables the whole thing so you cannot turn it on anyimore. And the first fuse is just to prevent it to be damaged. But its just speculation from my part
@@zozozoli I've had it trip the thermal fuse on the magnetron only, at least once. When this happens the microwave will function like normal except that the magnetron won't kick on. There's a bit of a subtle sound when this happens, like the motor slows just a little and then picks back up, but most notably, what you're trying to heat, won't. In this experiment you can see the current draw rises first when the microwave is turned on, and then a second time like a second later. I think this is the magnetron turning on separate from the rest of the microwave. Edit: I've never replaced this fuse so I think it's one of those self resetting ones.
Simple and concise little test, but good to know about. Also, the comment that the microwave wasn't heating anything in the glass video is kind of silly since it is heating something!
Conclusion is wrong and your motor analogy doesn't work. The power draw is very similar in both situations. With water inside the oven, you know most of the energy is used to heat it up, with nothing in the microwave you're still drawing like a 1100W, where do you think all that energy (heat) is going? It's heating up things that shouldn't be heating up. It may or may not be causing damage but you don't know that for sure. All that energy is unaccounted for.
@@FreedomOfDegree That's definitely going into the water, which doesn't change anything. You're so hung up the 1 amps but you're completely ignoring where the other 10 amps is going. What do you think, that only 10% of the power a microwave draws is used to heat food? No, microwaves are 50% efficient, so half the power goes into the food or water as heat. When there is no food to heat and you're only drawing 10% less power, where do you think the remaining 40% goes to?
@@CASTSTONE well, by design, the microwave must be able to support that 40%, otherwise it would damage itself even with the water inside of it. I'm no expert, but in an AC circuit there's reactive power. It's caused by things like inductors and capacitors. There's both a huge capacitor and an huge inductor (transformer) inside and I'm inclined to believe that they are not expressly designed to counteract the effect of reactive power, but rather necessary for the magnetron to function. There's also a couple motors in there for the fan and spinning plate (more inductors though they could be DC, I haven't checked). I don't think my ammeter differentiates between current drawn from active or reactive power, so I'd wager some of that 10 amps is reactive. Not sure how much though.
Reflections off the metal walls create standing waves, which are either absorbed by something in the chamber or end up bouncing back into the magnetron... It's like running a radio transmitter into a high SWR
I mean, wouldn’t the point of adding water not be to reduce load, but to serve as a heat sink? If the heat is going into the water, it’s not going into the microwave body. However, that would at the same time reduce the power into the glass, so it probably wouldn’t actually help much.
@@Top-Code I don't think the body of the microwave is being heated by the microwaves. My microwave is a piece of garbage and overheats like crazy. I think its ventilation is the problem. I never thought that adding the water might actually reduce the heating that the glass was receiving, but it makes sense.
@@FreedomOfDegree Where's the energy going then? It's a faraday cage (and there are regulations about this), so it's not pushing 800 watts of microwaves out to the room. And it is drawing power, assuming you're on 120v, so that would make for over a kilowatt going in! I not sure the cooling system would be capable of dissipating all that power without overheating. I checked my µwave: input power: 1280W, output: 800 W. That would make for an extra 800 W of heating somewhere inside the oven on top of the 480w in normal operation. Almost triple. No way the manufacturers aren't cheap enough to design that much of a margin in an affordable consumer device :D I remember hearing something like _if the microwaves don't get absorbed by food, they bounce right back in to the magnetron, and it will overheat and break_. Maybe you ought to put a temperature probe on the magnetron's heatsink, and see if it heats up more with no load? Obviously, be really fucking careful if you do that, and do research beforehand if you haven't got experience with high voltage electronics! (or just don't do that, it's genuinely really very dangerous) Actually, now that I checked online, the transformer alone draws around 10 amps of reactive current with no load. Does your meter show reactive current? Maybe the missing energy is being dissipated as heat in the transformer core, from hysteresis losses? They're built really cheap and saturate like crazy. Maybe measuring the temperature of the transformer would give an answer? Then again, does the magnetron stop outputting more microwaves it it "sees" a bunch of radiation already bouncing inside the oven? I don't think so. But I don't know enough about magnetrons to tell, I'm just spitballing here. Also, in the beginning, you got loaded/unloaded backwards. That glowing wire was an example of a load. (or maybe I misunderstood, crazy brain fog rn :)
@@Thrustmaster64 I don't really know exactly how the microwaves are dissipated when there's nothing inside. When I made glass in the microwave it was very clear that a lot of that energy was being dumped into the glass. But the walls of the microwave don't get red hot and melt. Not sure if it's because it's metal and radiates the heat to the environment better (I did encase the glass in insulation to prevent just that). When the magnetron is running, it definitely creates standing waves inside the microwave's body. These waves seem to oppose the generation of additional waves, which is why it consumes less energy when it is empty. I'd bet my ammeter measures reactive power while also applying a small load to the circuit. The burning wire in the beginning was meant to represent the amount of power that is drawn when a circuit has a very small load. All wires will load the circuit some, I just used a nichrome wire so that I could more easily show how high currents can generate a lot of heat very quickly.
@@FreedomOfDegree I'm pretty sure that a low resistance load is a heavy/large/high load, and a very high resistance is a light/small/low load. I mean, if I'm carrying a heavy load on my back, it will load me down and I'll have a hard time and expend a lot of energy, just as if a circuit has a load connected that's very heavy, it will struggle with the high current demand of that load, and a lot of power will flow. When I was younger I had a similar thing with open/closed circuit (avoin/suljettu piiri); for the longest time I thought that an open circuit means the current is flowing, because gates are open, you know? In Finnish, if you turn off a device, you can say "sulkea", which also means "shut". (Or "laittaa pois päältä" which would be "put away from on top", literally :D) "Sulje ovi" = "close the door", "sulje tv" = "turn off the tv" It took a good while to get used to!
@@Thrustmaster64 you're right. I definitely got them mixed up. It makes sense in the context of the motor. With no load on the motor, it draws less electricity. But when I load it, it starts to draw more. It's super confusing to me to add a "small load" to a circuit and then add the largest resistor you can find.
In my opinion, assing water while making glass will resuce the amount of heat being put into the glass and will instead dump that heat into the water, causing it to eventually boil and add humidity to the chamber. Which may not be good for making glass or the chamber in which you make it. I'm new here, so I haven't seen your apparatus for melting glass. Is it one of those graphite kiln things that go in a microwave? If so, the humidity feom adding water may damage the graphite once the water starts boiling and putting off steam. But id be more worried about the wayer stealing energy from the kiln, or whatever it is you use, making the process far less efficient for melting glass. You can only dump so much energy into it, why waste that energy on heating water? If the kiln/whatever you use is already absorbing heat/microwaves, then a thing of water should not be needed. On another note, it seems that no matter what, it still uses the same amount of energy, even empty. So the microwaves are still being absorbed by something. If not the walls, then something else inside the microwave. They're not getting out and hearing up things outside the microwave, so they're being absorbed inside of it somehow. So I'd venture to say that it's best to not run one empty. But that said, if your glass making apparatus is working properly while being heated by the microwave, then you shouldn't need to put anything else in there. Melting glass produces a lot of heat. Do you think that just the heat from the glass radiating off into the microwave is causing the overheating issues? I mean, it is a sealed box with red hot glass inside, that heat has to go somewhere as it radiates off. Judging by what I've read of tour comments, I'd also guess that it's simply a poor cooling design on the microwaves part. But that said, i doubt the microwave was designed for things to reach such high temperatures inside of it. Does it overheat when heating anything? Or just the glass? Looking forward to future videos. 😃
maybe the water could absorbing some of the microwaves so they aren't heating the components from the inside? even if the reflectivity of the microwave walls is 99.9% almost instantly all the energy will get absorbed by them and radiated to the inner components
That is a good point. I don't know why the microwaves don't heat the metal walls as well as they do other things, especially since they are presumed contained. However I do know that they don't heat up very much. Most of the heat comes from the electrical components driving the microwave. Mine overheats substantially more than it should because of a poor ventilation design.
@@FreedomOfDegree ah yeah that makes sense, the ac to microwave converter is probably the least efficient part. Maybe the microwaves do heat the walls but they easily conduct the heat away to the shell
With water the energy created is heating the water. Without water, where do you think the energy created is going? It's a rather simple answer as it simply doesn't leave it's confined space.
@@precisionguesswork5394 I don't think it's quite that simple. If we assume it doesn't leave the confined space, where does it go? Into the walls most likely, but the walls don't get red hot. It could be that they radiate the heat to the environment more effectively than say the water or glass from my other video. Also, there's a 1 amp difference in current draw between the empty microwave and the full one. Since the water is definitely absorbing energy from the microwaves, this means that somehow, the emptiness of the microwave is impeding the flow of electricity. My hypothesis is that because the microwaves are forming standing waves inside the heating chamber, these standing waves are opposing the production of more microwaves, thus less current is drawn.
@@FreedomOfDegree I believe the waves are reflected off the interior walls and strike themselves much like spark knock in a gasoline engine. I also believe there is a backlash to the magnetron causing heat much like the heat created when air is compressed with no where to go.
@@precisionguesswork5394 I think I see what you're saying and I think we agree. As a given microwave returns to the magnetron it is returning in just such an orientation as to oppose the creation of additional waves. In your analogy, the spark and fuel/air are like the magnetron and the piston represents the microwaves. I'm not sure that the designers of these microwave ovens took too much care into preventing such an event. Especially since they typically have the rotating plate to try and reduce hotspots. This would certainly alter any standing wave pattern that would normally form, and alter the phase of any returning microwaves. So I reckon that the developers designed the magnetron to be strong enough to handle returning microwaves, no matter the phase. Though I do concede that with nothing in the microwave, the standing wave pattern will likely cause uneven wear on any components that interact with them.
@@FreedomOfDegree I go back a few years, and as I recall in the mid 80's, microwaves had a warning not to run them empty. I also recall that through the years they've changed magnetron shielding as well as had some type of apparatus that altered, or rotated the direction of the waves that didn't last long to my knowledge. Many people kept a small glass of water in a back corner to prevent damage.
@@precisionguesswork5394 all my life I've been told to not put metal in the microwave because of the vague risk of "damaging it." Recently however, I've seen professionally sold microwaveable (something like) Tupperware. It held like a tv dinner, but the bottom part was fully metal (it felt like aluminum). It worked exactly like the cardboard ones. I've seen others on RU-vid experiment with metals in the microwave. Notably aluminum foil likes to generate plasma if it's crumpled up. Steel wool ignites as if struck with a battery. If I had to guess, the water content of the dinner as well as the heat conduction of the aluminum was enough to quell any misbehaviors. But I don't think the sheer presence of metal in the microwave will damage it. This is my long way of saying, it might be worth looking into exactly where the idea "running a microwave empty can damage it" came from.
