What the heck is an ELECTRET?
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- čas přidán 16. 07. 2024
- Everyone knows what a magnet is. But have you ever heard of an electret? Yeah, me neither! In fact, there's an entire branch of science/engineering that gets very little attention these days - outside of very specific applications that like 3 people know about. Join me for a look into the amazing world of electrostatics!
Goodies in the vid:
- 9to5science.com/electric-fiel...
- "Electrostatics: Exploring, Controlling and Using Static Electricity" by A.D. Moore - amzn.to/3JTbSAz
- "Electrostatic Motors: Their History, Types, and Principles of Operation" by Oleg Jefimenko - amzn.to/3DcUOle
- en.wikipedia.org/wiki/Electret
More techie tips: scottiestech.info - Věda a technologie
I think the biggest issue why electrets are pretty unpopular for mass manufacture is the fact that it's is way harder to create a strong electric field compared to making a permanent magnet. You can make an electret in a similar fashion to a magnet, simply by raising the material to its curie point (or whatever it's equivalent is called for a dielectric) and then applying a strong field (you can melt the material too, but its not always necessary and it reduces repeatability). The big difference is the fact that a magnetic field doesn't suffer from electric breakdown meaning you can generate a ginormous magnetic field in a small volume. With electric fields, you suffer from the breakdown voltage of the dielectric you are trying to charge, so there's a hard limit on your field strength. Other manufacturing methods (charge embedding, corona charging, etc.) are usually limited with depth of penetration of the materials, limiting you to charging only very thin films which, again, have little applications (one of which, like you said, the electret microphone).
Since magnetic fields and electric fields are so inherently connected, usually whenever you find an application that might need an electret to create a potential difference somewhere, it is often possible to figure out a way to do it with a magnet and a coil instead. Whenever someone really needs an electric field, usually a high voltage between two plates suffices as well and probably is a cheaper alternative (electrostatic speakers for instance). Also in niche applications, since you are limited to mostly plastics, they're hard to use in high vacuums, higher temperature environments, etc.
I do want to say it IS an interesting field nevertheless, and weak electrets are also pretty doable to make if you have access to a high voltage power supply. A super well-known and researched material is the use of carnauba wax. If you put a high voltage between two plates and pour in a mixture of 50/50 carnauba and colofonium resin (if it's too brittle you can add stuff like paraffin or beeswax), let it cool, and solidify, pull it from the mould and let it sit for a while to stabilize. I've managed to make my own electrets with the best ones having an electric field strength of about 1kV/mm (past this, I kept getting breakdown between the two plates). I used those to play around and make a guitar pickup with them. You can use an electret to make a capacitor with permanent charge, using either a conductive string as one of the capacitor plates where the vibration changes the distance, thus also the capacitance, or using the non-linear relationship of the placement of a dielectric between two capacitor plates to change the capacitance with a nylon string.
It was purely for fun, I still plan to document the process so it's repeatable for everyone, though I did not find any benefit compared to whatever already is on the market besides it being a gimmicky thing.
The reason is that permitivity is so bad. Only good at super short range.
Please look at my electret powered electrochemical cell.
m.youtube.com/
Just drop 2 copper plates in NaOH or KOH and start playing. I recommend gluing some glass rods on to them.
@m.e.8273
Well that about answers _my_ questions! Thanks!
@@m.e.8273 You are right. Magnetism is so much more convenient. I sometimes figure out how to do things that are not yet possible. I can make an electrochemical cell using magnetism if only I find an ironic liquid in which one ion is ferro magnetic.
Jefimenko has several other great books...he has a textbook on electricity and magnetism...then some much deeper ones that continue on. Definitely a great genius to read.
Fascinating, oh yes another lot of information kept in the shadows. More on this please, you make techie stuff understandable.
If it is still possible to get into the old Keelynet files, there's heaps on electrets.
Knowing the price of rear earth materials going into building of motors this topic is the future
I remember first seeing "Electret Microphone" in I believe 1981 82. My first cassette tape recorder.
Electrostatic loudspeaker was a thing around 1960. Quite expensive.
HiFi loudspeaker the size of a thin light box. I remember reading about them as a teenager.
Scottie good to see you , thanks for your work 😊
Great video; I have also been looking into this topic and really want to call a safety issue to your attention. It turns out wax electrets do not need to be made from molten wax, but are more reliably and safely made by forming the wax first, and then electrifying it at 70C, while it is still solid. Molten wax can be a danger if the power supply has too much power as its resistance goes down with temperature, and can run away into a fire without current limiting. You can read all about this in "Experiments on the Carnauba Wax Electret" (1955; Gerson & Rohrbaugh)
You're very funny! I once nailed a screw into the wall & then wondered why there was a crack in the wall, so all the rest of it about rosin etc, I tune out. I have no mechanical gene apparently. But as always thx Scottie.
Love the singlet 👌🏼
A cubic meter is a pretty big motor ....
A cubic metre is different to a metre cubed...
To make things easier use 2 instead of 1 ...
Builders merchants have this situation a lot... 😻
@@mySeaPrince_ A cubic meter is 1 meter by 1 meter by 1 meter. this is about the size of a washing machine. and they are both the same thing.
@ScottiesTech
Please read other comments in this thread... 💥
Can you do a video on the difference between a cubic metre and a metre cubed...
As I said in my comment use a unit other than 1 ie 2 as it can make more sense..
In my time I've had this situation.. also... Builders Merchants have this issue with people ordering materials like sand etc.. one person tried ordering 12m3 of sand .. they had a little bit of a shock at the price, particularly the cost of the number of lorries required.
(I did notice you thinking it through in the video)
Another 'Area' to 'Cover' is 2 dimensions ie slabs and carpet 😻
We dont know if the power curve goes linearly or not down to a 1 HP motor!
True, but the given the nature of his rather surprising comment at the end of the book...
Scott y. To captain k...me electrates cant take much more!
Thank You . . .
Do you know of any lectures dealing with nanobubbles which are created with electrostatics? The paper I read is called Massive generation of metastable bulk nanobubbles in water by external electric fields.
I haven't been able to find a video explaining or talking about how to build this. Would you be up for creating a video building / explaining this?
👍👍👍.Thank you
Awesome Channel... I just found you and Subbed.
Have missed your videos! Pray marriage is agreeing with you❤ be blessed🙏
Stay well and be safe 🙏💖☝️
Texas Nana 🤠
Psalm 91
💥
More videos please...
something similar..
Year's ago I looked into Stirling Engine's...
I think why they aren't popular is there is a so called easier option..
that serves the majority...
and is addicted to something that is taxable....
tin foil hat time 🐱
Supplying 1000+ volts .. DC? .. would be fun..