My dad lost one of his hearing aids and asked me to help him find it. His remote was able to connect to it anywhere in the house. I wrapped the remote in foil with just a small opening at one end, and it made a directional sensor. After about 5 minutes, I found it in the kitchen on the floor behind a chair leg. Thanks Faraday!
Back in 1981 I worked on a laser light show from the top of the Empire State Building. They were broadcasting tv and radio from antennas there which generated massive amounts of RF interference. None of our electronics worked, including all our test equipment and the galvanometers we used to steer the laser beams. So I took a cab down to Canal Street where you can get all sorts of weird surplus tech stuff and bought a bunch of copper sheeting and copper tape. I had our guys wrap all our equipment in copper, leaving small holes for the laser beams. Sure enough, it all worked! Something less fancy might have worked too but I only had a few hours before the stores closed so I tried to come up with a solution that had the best chance of success.
@@1st_ProCactus Thanks! The diagnosis and solution were all me. I had graduated with a BS in physics a couple of years before I took the job. While I was an undergrad I worked in a physics lab about 15 hours per week so I was very familiar with RF interference and shielding. Of course I had learned about Faraday cages in my E&M class. I knew about copper tape with conductive adhesive from the physics lab. I felt lucky to have found some down on Canal Street. The best part, by far, was I stayed the entire night alone on top of the Empire State Building "to watch over the equipment". I got to see the sun rise over Manhattan. There is a beautiful view in every direction but you normally can't see it all at once because the place is filled with tourists. It was one of the most memorable experiences of my life.
@@1st_ProCactus No. We needed to open them up to service them and clean the optics. In most situations there was no need for the copper because the aluminum cases usually provided ample shielding as Kathy demonstrated. It was confusing that the aluminum cases did not provide enough shielding. This is why I was called in. I figured we were getting bombarded by tv and radio broadcasts from close range so I decided to try copper because it's a better conductor. If the copper didn't work then the show would probably have been canceled. There is also stuff called "mu metal" for shielding magnetic fields but that is more expensive and harder to find. The copper looked spectacular! It felt like they were tributes to a Sun god. The aluminum was anodized or painted black which helped camouflage the equipment in normal situations, like nightclubs. We also did exhibits at the (little known) 1982 Knoxville World's Fair. I wrote a byte-code language to program the shows that ended up being the inspiration for Shockwave and Flash. I flew down with a technician the night before opening day. We got up early and climbed over a fence to get inside the fair grounds and started putting our equipment together. We were still fixing things while the first audience filled up the auditorium. A leg had broken off an IC and my tech soldered on the lead from a resistor to replace it. He plugged in the IC when the audience was already in place. We hit the "start" button and by some miracle the show started!
I studied medicine in the 70’s. Now does a set of 3 Tesla coils mounted within less than a foot of each other in X, Y, Z configuration make any sense o anyone? My simple minded conclusion is at best the whole thing would arc & “self fry” . Just in case this didn’t occur, the fields would cancel each other and nothing would happen no matter how strong the field was. Can anyone with a physics background explain this configuration?
Back in the 1960s almost every tall building in NYC was supported by iron beams on a 16' center to center and similar beams in the floor. All of us ham radio operators knew (but didn't know why) that using the six meter band was the best option for communicating from within a building without an exterior antenna.
@@tedstriker5991 Maybe the diagonal distance crossing the steel rectangle made by the horizontal and vertical beams (think diagonal monitor/screen measurement).
I was an Extra class, did mostly 15 meter, some 2 meters & successfully experimented with phased helical arrays in 1.2 GHz with moonbounce with 250 Watts!
it didn't "get out", instead, it turned the building into an antenna via inductance. The magnetic field created by the radio inducted current into the iron beams, which then released the current back out as radiation, or a radio wave. it's similar to how you can place a piece of iron next to a radio, and if it is the correct length, the radio will pick up the signal better. At least, this is my understanding of it. I may be wrong, and if so - please do correct me so that I have a more complete understanding. TIA. :)
Bridge superstructures block AM radio because the wavelength is longer than the "holes" in the superstructure. AM radio is essentially 200 meters and longer...
Very few people can bring electrical engineering alive as you do Kathy. Your insights and slides make it not only informative, but your passion makes it incredible. You are awesome.
I've often been amazed at the insanely primitive means these geniuses used to formulate their reasoning and subsequent equations from. THIS video boggles the mind in that direction even more. The discovery of electrical principles and properties was an incredibly slow slog-- detection of anything required a detector, so... how do we detect that... thing? Truly fascinating! Thank you, Kathy!
Im currently an ee student that never realized the context of all the people whose names today we use as reference points. And I feel the subject matter is more clear now that I know how it was discovered. Im really glad I found this channel
I'm glad you found me too. I am constantly surprised how looking into the history has deepened my understanding of the subject. I have a TON of EE videos so feel free to watch more (hint hint)
Way Cool! I do have a question though. I mean, if I may? I've seen tesla coils with a faraday cage, and they use the tesla coil(s) to make sound akin to what is seen in the movie The Sorcerer's Apprentice. I'm curious as to how the sound frequency would be ran through the tesla coil, so that the lightning vibrates the are to make the sounds?
@@michieal221 Sure… The Tesla coil is a pulsed device in which the pulses are produced by the mechanical spark gap or in electronic coils by a “H” bridge of semiconductors. In either fashion, the energy stored in the primary capacitor of the Tesla coil is dumped into the primary coil thereby creating a radio frequency resonance that microseconds later ends up as lightning from the top of the secondary coil. This dumping of the capacitor can be at any frequency, usually frequencies in range of human hearing. A mechanical synchronous rotary spark gap makes a fixed frequency sound: BBBBRRRAAAPPPPPPP! Electronic coils, however, can vary the frequency of the capacitor dump so much so that tones or “music” can be heard from the resulting arcs.
As a sixty year old, I still love to understand since and physics. Your understanding and visual explains are excellent and truly enjoyable. Thank you very much, and please continue to enlighten and entertain.
When I was at Bell Labs back in the 1980s I watched with great interest as they built a huge Faraday cage in one corner of the building and proceeded to install a lab in it. It had a vault door with a combination lock to enter. Those of us without a need to know knew it was for some government project but that was about it. One day I met a researcher who worked in that room and asked her if the cage was to keep signals out or to keep them in. She just smiled and said, "I can't tell you that."
A similar room was built in McKee Hall at the University of Northern Colorado, but for testing psychic phenomena. Interesting cross discipline uses, eh, what (Watt?)?
Bell Labs in Middletown NJ was built in a way that the whole building is a huge Faraday cage. As a courtesy for employees they put in AT&T cell service. No other cell phones from other companies work inside.
When we did some measurements on a micro wave radio link equipment situated near a short wave radio station (Radio Kootwijk) we used a Faraday cave to block these shortwaves. It was made from chicken wire. We also had a fm radio playing inside the Faraday cave. If we closed the door the music dumbfounded, if one opens the door just one centimeter we enjoyed the music again.
Being into electronics and radio, Michael Faraday is one of my absolute favorite scientists. I get perturbed that he was dismissed because he did not have great formal credentials or the mathematics skill of James clerk Maxwell. I would much rather have natural intuition about some thing, then I would simply have mathematical-knowledge to use in deducing them. I find that when I build various experiments, I’m not really using that much formal methods but more of an intuitive and empirical methodology. Most all of the components that you will use in electronics, suffer from being non-ideal implementations; so this allows for empirical experimentation to be much more valuable because you know when you make something work, it works! One of the greatest attributes that you can have is an innate curiosity and appreciation for the natural world around you…
Super presentation Kathy, Wonderful device the Faraday Cage, Back in the 70's I spent some time in a University Metallurgy Dept. They had developed a spark erosion technique for making complex metal shapes, however whenever it was used, it wiped out the communication system at the local Airport some 30 miles away. The solution, put the whole thing in a Faraday Cage. Just as today, small Faraday Cages are being sold to keep "Keyless car fobs" in to prevent thieves from picking up their radio signals and cloning them . Science against crime, wonderful!
From many years as an electronics technician (I often say "electron pusher"), I definitley remember many occasions of feeling the hairs of my body moving when near a high voltage source. An interesting feeling, and a warning of nearby danger.
Newton, Faraday, Maxwell, Rutherford, Einstein /Plank, Shroedinger /Bohr /Dirac /Heisenberg. Each step needs more and more genius power to grasp: Shoulders of Giants. Thank you for helping us take little steps and bringing science to life so clearly.
Just found your 'stuff' by accident Kath. Could have done with you as my instructor when, as a 30 Y/O ex Brit Army Sergeant Major, I became a civvie, through choice, and struggled to complete my first Bachelors. ( Electronics ) but you can't get into the field without understanding the tenets of electricity! Now live in Australia's lower 40, Tasmania down in the 'roaring 40's'. Retired now, but enjoy your 'touch', Thanks!
A lot of stuff to think about. I always am amazed that people were able to reach such astounding conclusions from data obtained by such crude experiments. Thank you Kathy. I appreciate your work very much.
Just realized something about electron microscopes and why they have to 'f'ix' what they are focusing on. The wavelength of the electrons has to be very short so wat they are looking can be observed. However this means the beam of electrons, is so high energy, the beam destroys what is being observed. They 'fix' with various compounds so they can shoot electrons at it and use computers to visualize what the electrons were reflected off. Of course there are transmitting electron microscopes, but the issues are very different.
I learnt about Faraday cage when I was 11 years old. As I grew up, I discovered that it is not part of general knowledge. This gave me an unique opportunity to exploit it to my advantage when I got a mobile phone years later. When I wanted to avoid calls from somebody (which sometimes but not always meant my parents), I would wrap my mobile handset in aluminum foil and blissfully avoid all the external world.
@@nHans switching off or "flight mode" conveys a voice message that this number is switched off. However on wrapping with metal foil, the message is that network is out of range. Perfect alibi.
In 1990 I was a biomedical engineer at a southern CT hospital. The electromyography lab (patient muscle nerve diagnosis through measuring the millivolt nerve signals through needles and amplifiers). The lab was in the basement of the hospital and working fine. They were moved to the 8th floor facing Long Island Sound. Day 1 when the needle was inserted into the patients' skin, WOKO FM blared out of the speaker on the EMG machine. The 1 MW WOKO transmitter was a mile away. We had to wrap the entire room in grounded copper screening to attenuate the signal.
I absolutely love learning via your technique of incorporating the facts of a particular subject and give it the added benefits of also learning the history behind it - amazing work. Thank you :)
Very good sikhswim :-) The airplane windows exclude waves "beyond cutoff" frequency so tiny waves like light an microwaves pass thru but big wave like AM or FM broadcast are blocked.
Thank you Kathy. This is a great explanation. You have a knack, and throwing in the historical stories behind the science make it a joy to watch your videos!
Loved every bit of explanation in this video. The history, the physics, the examples all came alive in an enjoyable and informative manner. I say this from a standpoint of someone who holds a degree in physics and works in the field of physics education. Thank you, thank you for such a wonderful work. 👌🌹👏
Without understanding the physics, my father knew the safest place in a lightning storm was in the car. It stuck with me all these years. The college level physics and electrical engineering course I took did not explain faraday cages as well as you did. Thanks!
A car is not a faraday cage, it is a classic lightning protection structure (aside from the glass). Faraday cages are radio tight. Lightning hardening is the art of giving lightning a best path of our choice. I was the lightning hardening guru for the IT Field Services department of a Fortune 100 electric company before I retired. One caveat: cars made primarily from composites are no protection against lightning - you might as well be sitting on a chair.
@@Kathy_Loves_Physics I sometimes will use other fake names when directing really bad movies such as Rian Johnson or J.J. Abrams so look for me there too
I am so much looking forward for a video on Oliver Heaviside! I'd love to understand what the differences are between his formulas and Maxwell's formulas. Go for it Kathy!
When I was a newly graduated electronics technician my first job was in a factory where we made garage door openers. This involved a hand sized remote control - the transmitter, and a quarter shoe box sized receiver that triggered the door opener mechanism. These operated at around 27 MHz where there is a channel near the CB band reserved for low power (< 5 Watts) devices. Part of my job was tuning the transmitters and receivers as they came off the assembly line - tweaking tank coils to the precise crystal controlled frequency. There were days when the RF band was so noisy it was impossible to do my work, so the boss made a beautiful Faraday cage using wide copper strips around the frame and copper screening on all 6 sides of the cube, all of it soldered together, with a door that closed making full electrical contact. I worked inside that cage from then on. However - don't get the idea that these things are perfect. They are far from it. They attenuate the RF by some number of decibels, rather than drop it absolutely to zero. There were still days when the RF interference made my work difficult, though far fewer than before.
There are versions of Benjamin Franklin‘s work that have been updated to have modern spelling but I prefer the originals partially because I really like those fs where I’m expecting an s.
Great explanation again, reminded me of our physics lab technician who strolled in during the Van Der Graaf generator session in school, he had long frizzy ginger hair and thinning on top. he laid hold of the generator and the whole class laughed as his hair formed a weird shape. Great man new exactly what he looked like and new what would happen. Cheers
Love your stuff Kathy. I just pre-ordered your book from Amazon. Incidentally I took an online static electricity dangers course this morning I work in electronics and the course did mention that Franklyn discovered two two types of electric charges which he named plus and minus. However the history of the names conductor and insulator wasn't mentioned and it even more interesting.
I'm a science communicator, and I love everything about this video. Also, I keep thinking of those videos that show teachers standing at the far end of swinging pendula with bowling balls on them to show how much they trust physics by risking a bowling ball smack in the face. Frankly, I think being willing to get struck by lightning shows a far greater degree of scientific trust and general badassery -- Bravissima!
I’ve been meaning to thank you, I was a poverty stricken kid growing up, missed out on a comprehensive education, I made up for some of it later but my Maths and Science has always been deficient, your vlogs help!
So many people both historically and currently had a nontraditional path to their learning. Congratulations to you for learning on your own and I am honored to be a part of it.
@kathylovesphysicsandhistory, I LOVE the fact you used KFOG as the example of a radio station! My all-time favorite, I was truly bummed when they finally gave up and switched format. This video is really interesting - thank you for this and all the other ones you've done!
@@Kathy_Loves_Physics , yeah, I started listening to them a couple years after they switched to the rock format and they were my only station until they laid off most of the DJs for a youth invasion many years later. Loved Dave Morey and Ten@10!
This video just popped up for me, and as soon as I saw your channel's name, I knew it was gonna be good. I knew most of the physics already, and some of the history, but you filled in some wonderful gaps! Fortunately, not so much of the gaps that I can't get my favorite radio stations though :-) Subscribed!
Kathy I'm going to the Parrott library to watch your videos there excellent 👌 viewing. I'm about to try and convince our city that whiteboards or chaulk boards are a must. Need to wear my glasses. Anyway your videos are great and I do recommend them. Thank you
My favorite AM/FM Radio recipe. Delicious and tender variable capacitors and IF inductors that fall right off the ferrite core. I like just a little bit of vinegar-based sauce, some dipole slaw. Classic Carolina ham.
A Faraday cage will shield whatever is inside of it from electrical field but not from magnetic fields unless it is made out of special materials such as mu metal. CRTs were particularly sensitive to magnetic fields which distorts their image. I had one case where 10 milligauss caused problems with several. I had special enclosures made for them by a company called Amuneal at $1000 each about 30 years ago. Coaxial and triaxial shielded cables are exams of Faraday cages. For extra shielding thick ethernet backbone cable was quad shielded. 2 braids and 2 foils.
the Faraday cage we used in an electrophysics lab consisted of an inside layer of copper screen surrounded by an outside layer of the screen and both layers were separated by a wood frame. There was only one point of electrical contact maintained between the two. This formed a room for holding the electronic test and monitoring equipment so people could work inside that room while running the tests. The reason for the two layers was that a signal on the outside (like an eddy current) would generate a canceling field by the inside layer.
Your video is a wonderful and interesting overview of the Faraday cage history. Those early scientific investigators should be celebrated and studied in high school courses, in depth. Thank you and be well.
Ooh, was that before or around the time that the line between Philips and Magnavox got a little hazy? I know they put both names on many products for a good while.
Glad I came across your channel! I a m a. Physician and have seen old patients who were young engineers / physicists in the mid 50’s & 60’s.. Two concepts conveyed to me in the 1980’s stuck in my head all these years. 1) a vacuum quartz toroid contained (not filled) with a mixture of mercury, nano particles of iron, cobalt and barium, accelerated by external copper coils wound around the toroid and energized with increasing voltage, in the millions of volts would make the ferro-mercurial-cobalt barium mixture to flow faster and faster centered inside plasma ring This would after creating a corona effect around the tube, upon higher voltage & frequency were applied to the toroid, a white glow would appear as the radial velocity of the plasma reached near relativistic speeds. This field would keep expanding outside the toroid & experiment table . This would then cause the table where the experiment was being attached to lose weight and levitate. The explanation was that the “white field” would somehow “hide” M from gravity. Further speculation & experimentation led to the conclusion that the center of gravity of the object became “hidden” from gravity, therefore E= MC^2 would become E= c^2 or even c^ to infinity for that matter., while the field was present. Your thoughts? 2) Some sailors involved in installing very large Diesel generators in the USS Eldridge in the mid 1940’s 3 sets of 3 Tesla coils installed in front, middle & back of the ship. The generators were connected to transformers “capable of generating millions of volts “ . These were made by RCA. What is hard to comprehend , not being a physicist, is that the 2 meter long secondaries of each set of coils, mounted in groups of 3 in close proximity but strangely enough in an X,Y, Z configuration. Each coil hat its own primary separate from the other 2 coils in the set. Using the right hand rule, the fields would not reinforce each other. Also, using millions of volts in such close proximity would surely cause arching, which would certainly destroy the set it 3 coils . No arching was described during the dry run at lower voltage when the Eldridge was at port. There were also metal nets hanging from the deck of the ship over the sides that covered the entire hull . This was a continuous metallic net loosely fit around the hull. What are your thoughts? The USS Eldridge was the ship,used in the so called “Philadelphia Experiment.” Any comments on either odiferous the above accounts would be most welcome. Dr. T - MD
with regards to 1) not likely. Anybody who demonstrated a connection between electric fields and manipulating gravity would be swarmed by physicists seeing a clear path to a Nobel prize. Somebody or bodies probably got taken in by a scammer.
Much has been made of Faraday cages and EMP. Many suggest that grounding the cage is essential. Others claim in their “experiments” that absolute electrical sealing is required (no holes). This tutorial seems to debunk most of that.
Most of the damage from an EMP is high frequency so it does need to be sealed completely because those have very small wavelengks. Also, if you have a huge pulse you probably do want to have it grounded because if all the charge is there on the surface it can short circuit. However, for AM/FM radio you sure don’t need it to be solid or grounded. I talk more about this in my history and influence of the Faraday cage video as well as why I personally am less concerned about EMPs then many people are.
@@Kathy_Loves_Physics This is absolutely false, there is no reason that a grounded cage should protect better. It will aktually colect more charges than an ungrounded one in an electric field.
Grounding a faraday cage for EMP production is honestly quite trivial. And EMP is such a broad spectrum high frequency event that any grounding conductor that is more than 1/4 wavelength long will eventually add enough inductance to the system so as to make it as if it never really was grounded because the impedance of your grounding conductor increases with the length of the conductor. A lot of times hams on the upper floors of the building really struggle with RF in there radio room because they cannot get a ground connection that is short enough to be effective.
When I was new at the Fortune 100 electric utility I retired from, I worked in the radio shop. The shop had a faraday Cage about 6 feet high (I didn't have to duck) and 10x10 feet. It was copper clad plywood with two copper screen windows. As a ham radio operator for 20 years by then I was impressed we could key up a portable radio inside it and not be able to hear it outside the cage. It wasn't grounded - there would be no point to grounding it.
Unfortunately we live in an old stone built cottage with very thick walls. I suspect there's iron ore in the stone (there are the remains of a 200 year old blast furnace in the field near our home) which makes the rooms, crude Faraday cages and which makes mobile phone and satellite signals very weak. It didn't matter 150 years ago when the cottage was built but not so today :) John Flamsteed was born just a few miles from where we live in Derbyshire UK and the local school is named after him. When I want to measure anything electrical all I need to do is get out my digital meter - Faraday et al had no such option; that their primitive instruments worked well enough for them to derive their world changing discoveries is humbling. Thanks. You explain clearly and enthusiastically as always.
I occasionally talk about different chemists (Humphrey Davy, Robert Bunsen, Fritz Haber, etc) but usually only because of their influence on the history of physics because I’m a physicist and that is my area of expertise/interest. Sorry to disappoint. Kathy
I think you've done a great job in demonstrating the physics and history behind the Faraday cage, although I can't see clearly where you've got to the fundamental reason why E inside is zero: it's because the charges move around the conducting cage until they reach the lowest energy state when they can no longer move; when E = 0 inside the cage conductor. You can then prove mathematically via Laplace's equation that any volume enclosed by this boundary condition, aka an equi-potential surface, is a sufficient condition for E = 0 inside.
April 10, 2023 Provo, Utah FARADAY BAGS You teach me a lot. Beside the Faraday cage there is also the Faraday bag which is useful to courts and law enforcement. Many courts such as the California Superior Court do not allow anyone to have a phone in the court room (except the attorneys) and put all phones into Faraday bags and remove them from the bags when the person leaves. Faraday bags are also useful to law enforcement. Any time they take a phone the should turn it off and put it into a Faraday bag.This stops all communication with WiFi and cell towers. Putting the phone in airplane mode does not stop ALL communication. Certain maintenance operations with the service provider DO take place from airplane mode. In the recent Murdaugh trial in South Carolina. SLED (South Carolina Law Enforcement Division) had taken phone but only put them in airplane mode and while the phones were in the evidence lockers the towers communicated with them and changed some activity logs. This could have been avoided by putting them into Faraday bags.
My dad lost one of his hearing aids and asked me to help him find it. His remote was able to connect to it anywhere in the house. I wrapped the remote in foil with just a small opening at one end, and it made a directional sensor. After about 5 minutes, I found it in the kitchen on the floor behind a chair leg. Thanks Faraday!
Genius
cool, but that's not a faraday cage
@@LiviuGeleawhat is it then?
Smart
@@LiviuGeleanever said or implied that it was, only that the invention was inspired by faraday.
Back in 1981 I worked on a laser light show from the top of the Empire State Building. They were broadcasting tv and radio from antennas there which generated massive amounts of RF interference. None of our electronics worked, including all our test equipment and the galvanometers we used to steer the laser beams.
So I took a cab down to Canal Street where you can get all sorts of weird surplus tech stuff and bought a bunch of copper sheeting and copper tape. I had our guys wrap all our equipment in copper, leaving small holes for the laser beams. Sure enough, it all worked!
Something less fancy might have worked too but I only had a few hours before the stores closed so I tried to come up with a solution that had the best chance of success.
I miss the "real" Canal Street. 😥
Nice fix. Lucky you knew or someone knew what was causing it
@@1st_ProCactus Thanks! The diagnosis and solution were all me. I had graduated with a BS in physics a couple of years before I took the job. While I was an undergrad I worked in a physics lab about 15 hours per week so I was very familiar with RF interference and shielding. Of course I had learned about Faraday cages in my E&M class.
I knew about copper tape with conductive adhesive from the physics lab.
I felt lucky to have found some down on Canal Street.
The best part, by far, was I stayed the entire night alone on top of the Empire State Building "to watch over the equipment". I got to see the sun rise over Manhattan. There is a beautiful view in every direction but you normally can't see it all at once because the place is filled with tourists. It was one of the most memorable experiences of my life.
@@BitJam yeah sweet.. did you leave the copper clad on the boxes after ?, I'd be tempted to keep the copper look.
@@1st_ProCactus No. We needed to open them up to service them and clean the optics. In most situations there was no need for the copper because the aluminum cases usually provided ample shielding as Kathy demonstrated.
It was confusing that the aluminum cases did not provide enough shielding. This is why I was called in.
I figured we were getting bombarded by tv and radio broadcasts from close range so I decided to try copper because it's a better conductor. If the copper didn't work then the show would probably have been canceled. There is also stuff called "mu metal" for shielding magnetic fields but that is more expensive and harder to find.
The copper looked spectacular! It felt like they were tributes to a Sun god. The aluminum was anodized or painted black which helped camouflage the equipment in normal situations, like nightclubs.
We also did exhibits at the (little known) 1982 Knoxville World's Fair. I wrote a byte-code language to program the shows that ended up being the inspiration for Shockwave and Flash.
I flew down with a technician the night before opening day. We got up early and climbed over a fence to get inside the fair grounds and started putting our equipment together.
We were still fixing things while the first audience filled up the auditorium. A leg had broken off an IC and my tech soldered on the lead from a resistor to replace it.
He plugged in the IC when the audience was already in place. We hit the "start" button and by some miracle the show started!
I have an MSc in physics (1977) and studied all this decades ago, but you have the knack of making it all seem fresh again. Great stuff!
It
I studied medicine in the 70’s. Now does a set of 3 Tesla coils mounted within less than a foot of each other in X, Y, Z configuration make any sense o anyone? My simple minded conclusion is at best the whole thing would arc & “self fry” . Just in case this didn’t occur, the fields would cancel each other and nothing would happen no matter how strong the field was. Can anyone with a physics background explain this configuration?
Thanks for having the decency to acknowledge this lady's skills
Thanks for acknowledging this lady's skills
Back in the 1960s almost every tall building in NYC was supported by iron beams on a 16' center to center and similar beams in the floor. All of us ham radio operators knew (but didn't know why) that using the six meter band was the best option for communicating from within a building without an exterior antenna.
I don't understand. The 6 meter band has a wavelength of nearly 20'. That's greater than the 16' beam spacing. Wouldn't they be blocked?
@@tedstriker5991 Maybe the diagonal distance crossing the steel rectangle made by the horizontal and vertical beams (think diagonal monitor/screen measurement).
I was an Extra class, did mostly 15 meter, some 2 meters & successfully experimented with phased helical arrays in 1.2 GHz with moonbounce with 250 Watts!
@@bakedbeings it doesn’t have a full wave, it can be half wave or 1/4 wave…. Don’t understand how the rebar was set…
it didn't "get out", instead, it turned the building into an antenna via inductance. The magnetic field created by the radio inducted current into the iron beams, which then released the current back out as radiation, or a radio wave. it's similar to how you can place a piece of iron next to a radio, and if it is the correct length, the radio will pick up the signal better.
At least, this is my understanding of it. I may be wrong, and if so - please do correct me so that I have a more complete understanding. TIA. :)
Bridge superstructures block AM radio because the wavelength is longer than the "holes" in the superstructure. AM radio is essentially 200 meters and longer...
While FM, with it's 100 times shorter wavelength passes through.
Very few people can bring electrical engineering alive as you do Kathy. Your insights and slides make it not only informative, but your passion makes it incredible. You are awesome.
Thank you 😊
I've often been amazed at the insanely primitive means these geniuses used to formulate their reasoning and subsequent equations from. THIS video boggles the mind in that direction even more. The discovery of electrical principles and properties was an incredibly slow slog-- detection of anything required a detector, so... how do we detect that... thing? Truly fascinating! Thank you, Kathy!
Im currently an ee student that never realized the context of all the people whose names today we use as reference points.
And I feel the subject matter is more clear now that I know how it was discovered. Im really glad I found this channel
I'm glad you found me too. I am constantly surprised how looking into the history has deepened my understanding of the subject. I have a TON of EE videos so feel free to watch more (hint hint)
There's a documentary on YT..."Einstein's Big Idea"...a must see!
👍
EE electronics engineering tech? Cool good subject.
As the creator of the MegaZapper, I am thoroughly impressed with this presentation. Kathy, you really know how to put it altogether! Bravo! 👏
I was so hoping that you would like it, Jeff. Woo Hoo
Way Cool!
I do have a question though. I mean, if I may?
I've seen tesla coils with a faraday cage, and they use the tesla coil(s) to make sound akin to what is seen in the movie The Sorcerer's Apprentice. I'm curious as to how the sound frequency would be ran through the tesla coil, so that the lightning vibrates the are to make the sounds?
@@michieal221 Sure… The Tesla coil is a pulsed device in which the pulses are produced by the mechanical spark gap or in electronic coils by a “H” bridge of semiconductors. In either fashion, the energy stored in the primary capacitor of the Tesla coil is dumped into the primary coil thereby creating a radio frequency resonance that microseconds later ends up as lightning from the top of the secondary coil. This dumping of the capacitor can be at any frequency, usually frequencies in range of human hearing. A mechanical synchronous rotary spark gap makes a fixed frequency sound: BBBBRRRAAAPPPPPPP! Electronic coils, however, can vary the frequency of the capacitor dump so much so that tones or “music” can be heard from the resulting arcs.
@@jeffparisse4202 oh. That's really cool! thank you!!!!
As a sixty year old, I still love to understand since and physics. Your understanding and visual explains are excellent and truly enjoyable.
Thank you very much, and please continue to enlighten and entertain.
When I was at Bell Labs back in the 1980s I watched with great interest as they built a huge Faraday cage in one corner of the building and proceeded to install a lab in it. It had a vault door with a combination lock to enter. Those of us without a need to know knew it was for some government project but that was about it.
One day I met a researcher who worked in that room and asked her if the cage was to keep signals out or to keep them in. She just smiled and said, "I can't tell you that."
Almost certainly to keep them in.
It is not beyond the realm of possibility that the correct answer was: both
A similar room was built in McKee Hall at the University of Northern Colorado, but for testing psychic phenomena. Interesting cross discipline uses, eh, what (Watt?)?
Bell Labs in Middletown NJ was built in a way that the whole building is a huge Faraday cage.
As a courtesy for employees they put in AT&T cell service.
No other cell phones from other companies work inside.
When we did some measurements on a micro wave radio link equipment situated near a short wave radio station (Radio Kootwijk) we used a Faraday cave to block these shortwaves. It was made from chicken wire. We also had a fm radio playing inside the Faraday cave. If we closed the door the music dumbfounded, if one opens the door just one centimeter we enjoyed the music again.
i am unable to explain in words that how much i love her enthusiasm
Being into electronics and radio, Michael Faraday is one of my absolute favorite scientists.
I get perturbed that he was dismissed because he did not have great formal credentials or the mathematics skill of James clerk Maxwell.
I would much rather have natural intuition about some thing, then I would simply have mathematical-knowledge to use in deducing them. I find that when I build various experiments, I’m not really using that much formal methods but more of an intuitive and empirical methodology. Most all of the components that you will use in electronics, suffer from being non-ideal implementations; so this allows for empirical experimentation to be much more valuable because you know when you make something work, it works!
One of the greatest attributes that you can have is an innate curiosity and appreciation for the natural world around you…
Just do what Einstein did. Get your girlfriend to do the complicated math for you and take the credit.
@@DeezNutz-ce5seI have to admit, all my electronics designs were done by my partner, Casio.
Super presentation Kathy, Wonderful device the Faraday Cage, Back in the 70's I spent some time in a University Metallurgy Dept. They had developed a spark erosion technique for making complex metal shapes, however whenever it was used, it wiped out the communication system at the local Airport some 30 miles away. The solution, put the whole thing in a Faraday Cage. Just as today, small Faraday Cages are being sold to keep "Keyless car fobs" in to prevent thieves from picking up their radio signals and cloning them . Science against crime, wonderful!
From many years as an electronics technician (I often say "electron pusher"), I definitley remember many occasions of feeling the hairs of my body moving when near a high voltage source. An interesting feeling, and a warning of nearby danger.
The crazy thing is then when you get into a large faraday cage and close the door even though there’s holes you suddenly can’t feel that danger.
Newton, Faraday, Maxwell, Rutherford, Einstein /Plank, Shroedinger /Bohr /Dirac /Heisenberg. Each step needs more and more genius power to grasp: Shoulders of Giants. Thank you for helping us take little steps and bringing science to life so clearly.
Just found your 'stuff' by accident Kath. Could have done with you as my instructor when, as a 30 Y/O ex Brit Army Sergeant Major, I became a civvie, through choice, and struggled to complete my first Bachelors. ( Electronics ) but you can't get into the field without understanding the tenets of electricity! Now live in Australia's lower 40, Tasmania down in the 'roaring 40's'. Retired now, but enjoy your 'touch', Thanks!
Quick comment to you, Kathy. I really like your style of explaining things. You explain things well and keep the viewer's attention well.
A lot of stuff to think about. I always am amazed that people were able to reach such astounding conclusions from data obtained by such crude experiments. Thank you Kathy. I appreciate your work very much.
Just realized something about electron microscopes and why they have to 'f'ix' what they are focusing on. The wavelength of the electrons has to be very short so wat they are looking can be observed. However this means the beam of electrons, is so high energy, the beam destroys what is being observed. They 'fix' with various compounds so they can shoot electrons at it and use computers to visualize what the electrons were reflected off. Of course there are transmitting electron microscopes, but the issues are very different.
I learnt about Faraday cage when I was 11 years old. As I grew up, I discovered that it is not part of general knowledge. This gave me an unique opportunity to exploit it to my advantage when I got a mobile phone years later.
When I wanted to avoid calls from somebody (which sometimes but not always meant my parents), I would wrap my mobile handset in aluminum foil and blissfully avoid all the external world.
Assuming you didn't have "Airplane Mode" back then, you could simply switch it off? Same result, but you'd also save battery that way. 🙄
@@nHans switching off or "flight mode" conveys a voice message that this number is switched off. However on wrapping with metal foil, the message is that network is out of range.
Perfect alibi.
@@nHans : ah, but airplane mode doesn’t disable GPS , which will be used by apps to track your location history.
In 1990 I was a biomedical engineer at a southern CT hospital. The electromyography lab (patient muscle nerve diagnosis through measuring the millivolt nerve signals through needles and amplifiers). The lab was in the basement of the hospital and working fine. They were moved to the 8th floor facing Long Island Sound. Day 1 when the needle was inserted into the patients' skin, WOKO FM blared out of the speaker on the EMG machine. The 1 MW WOKO transmitter was a mile away. We had to wrap the entire room in grounded copper screening to attenuate the signal.
I'm surprised that was not included in the planning.
@@flagmichael Healthcare? Planning? VPs decided moves on unknown merits.
I enjoy the pace of this video. Thank you
I absolutely love learning via your technique of incorporating the facts of a particular subject and give it the added benefits of also learning the history behind it - amazing work. Thank you :)
Glad you enjoy it! I have become addicted to this technique - I really think it is so useful and inspiring.
@@Kathy_Loves_Physics I agree. Makes for a more enjoyable and memorable experience :) And you do it so well - that helps too
Very good sikhswim :-) The airplane windows exclude waves "beyond cutoff" frequency so tiny waves like light an microwaves pass thru but big wave like AM or FM broadcast are blocked.
Thank you Kathy. This is a great explanation. You have a knack, and throwing in the historical stories behind the science make it a joy to watch your videos!
Loved every bit of explanation in this video. The history, the physics, the examples all came alive in an enjoyable and informative manner. I say this from a standpoint of someone who holds a degree in physics and works in the field of physics education. Thank you, thank you for such a wonderful work. 👌🌹👏
Thank you so much, I’m so glad you enjoyed it.
Without understanding the physics, my father knew the safest place in a lightning storm was in the car. It stuck with me all these years. The college level physics and electrical engineering course I took did not explain faraday cages as well as you did. Thanks!
A car is not a faraday cage, it is a classic lightning protection structure (aside from the glass). Faraday cages are radio tight.
Lightning hardening is the art of giving lightning a best path of our choice. I was the lightning hardening guru for the IT Field Services department of a Fortune 100 electric company before I retired.
One caveat: cars made primarily from composites are no protection against lightning - you might as well be sitting on a chair.
Great video Kathy.
A thoroughly enjoyable video to watch, thank you for this wonderful history lesson!!
Glad you liked it
This is my new favorite channel!
Great video. I have bought the book. Learning the history makes it easier to understood the subject. Thanks Kathy.
You're a delight Kathy, I love your channel!
Thank you. So glad.
I love your name but I have to say many of your movies are a disappointment 😉
@@Kathy_Loves_Physics Well, I do make pretty bad movies but I do like to direct and post anonymously lol
@@Kathy_Loves_Physics I sometimes will use other fake names when directing really bad movies such as Rian Johnson or J.J. Abrams so look for me there too
I laughed out loud thank you
Very well done Ms Kathy.
You're great, Kathy.
Kathy "Hatts offf" for your hard work in compiling history and science. I would Love to hear about Quantam Computing in future if possible!!
I am so much looking forward for a video on Oliver Heaviside! I'd love to understand what the differences are between his formulas and Maxwell's formulas. Go for it Kathy!
Your video's timelines and details are the best . I really enjoy when you post videos.
So glad to hear it.
Very enjoyable. Former Navy ET and engineer. Thank you!
Wow and the knife was acting as an antenna while u poked holes. That was very cool to see. Thank you
When I was a newly graduated electronics technician my first job was in a factory where we made garage door openers. This involved a hand sized remote control - the transmitter, and a quarter shoe box sized receiver that triggered the door opener mechanism. These operated at around 27 MHz where there is a channel near the CB band reserved for low power (< 5 Watts) devices. Part of my job was tuning the transmitters and receivers as they came off the assembly line - tweaking tank coils to the precise crystal controlled frequency. There were days when the RF band was so noisy it was impossible to do my work, so the boss made a beautiful Faraday cage using wide copper strips around the frame and copper screening on all 6 sides of the cube, all of it soldered together, with a door that closed making full electrical contact. I worked inside that cage from then on. However - don't get the idea that these things are perfect. They are far from it. They attenuate the RF by some number of decibels, rather than drop it absolutely to zero. There were still days when the RF interference made my work difficult, though far fewer than before.
Love the explanation. So much more thorough and fun than freshman physics class!
What a great demonstration! Cathy, great job.
Thanks
This was awesome.
I want to get a copy of your book...I've preordered it... Can't wait to read it!!! I love your videos! ♥
Thanks (on both counts)
Good Video! I knew about the Faraday cage and how they work, but not the history of it.
Love your historical reviews!!
Boy, you sure are a treasure. Thanks for going deep into the history. You speak my language.
I'm 45 yrs old with no college education. Just wanted to tell you, that you are an interesting story teller. I'll bet your book is fascinating!
Thanks- I’m glad you like them and education comes from all places. 😊
I recall Smith Charts and studying signal propagation on a medium for RF. Waveguide and coaxial and balanced lines. Great stuff.
Interesting and worthwhile video.
i love when an f is used in place of an s, it reminds me of the ny public library inscriptions.
There are versions of Benjamin Franklin‘s work that have been updated to have modern spelling but I prefer the originals partially because I really like those fs where I’m expecting an s.
Kathy, you're very passionate and inspiring. Thanks for this and all the videos you've created.
Great explanation again, reminded me of our physics lab technician who strolled in during the Van Der Graaf generator session in school, he had long frizzy ginger hair and thinning on top.
he laid hold of the generator and the whole class laughed as his hair formed a weird shape.
Great man new exactly what he looked like and new what would happen. Cheers
Love your stuff Kathy. I just pre-ordered your book from Amazon. Incidentally I took an online static electricity dangers course this morning I work in electronics and the course did mention that Franklyn discovered two two types of electric charges which he named plus and minus. However the history of the names conductor and insulator wasn't mentioned and it even more interesting.
Thank you. The story of conduction and induction is fascinating, isn’t it?
I'm a science communicator, and I love everything about this video. Also, I keep thinking of those videos that show teachers standing at the far end of swinging pendula with bowling balls on them to show how much they trust physics by risking a bowling ball smack in the face. Frankly, I think being willing to get struck by lightning shows a far greater degree of scientific trust and general badassery -- Bravissima!
I’ve been meaning to thank you, I was a poverty stricken kid growing up, missed out on a comprehensive education, I made up for some of it later but my Maths and Science has always been deficient, your vlogs help!
So many people both historically and currently had a nontraditional path to their learning. Congratulations to you for learning on your own and I am honored to be a part of it.
Your the only one that I can understand this wonderful information, Thank you!
Just finished your book 'The Lightning Tamers'. Really enjoyed it, and particularly how it put Tesla into proper perspective.
@kathylovesphysicsandhistory, I LOVE the fact you used KFOG as the example of a radio station! My all-time favorite, I was truly bummed when they finally gave up and switched format. This video is really interesting - thank you for this and all the other ones you've done!
They were such a great channel. I was a total foghead. Am still bummed about it.
@@Kathy_Loves_Physics , yeah, I started listening to them a couple years after they switched to the rock format and they were my only station until they laid off most of the DJs for a youth invasion many years later. Loved Dave Morey and Ten@10!
Always love your history lessons!
Great video. Thank you. Brings me back to my electronics training in 1980 while in the Royal Canadian Navy.
This video just popped up for me, and as soon as I saw your channel's name, I knew it was gonna be good. I knew most of the physics already, and some of the history, but you filled in some wonderful gaps! Fortunately, not so much of the gaps that I can't get my favorite radio stations though :-) Subscribed!
You are very good at explaining interesting topics
Fantastically interesting. Thank you for the detailed and the passionate story telling❤!
Kathy you rock! Thank you!
Wonderful video. Thank you Kathy
Professor, I salute you. Very impressive presentation.
Kathy I'm going to the Parrott library to watch your videos there excellent 👌 viewing. I'm about to try and convince our city that whiteboards or chaulk boards are a must. Need to wear my glasses. Anyway your videos are great and I do recommend them. Thank you
Thank you for properly crediting the inventors and sources of inspiration there. I had no idea based based on the basic history taught at school. :)
Enjoyed this video, but really looking forward to the next one :) Thanks as always.
Me too. I’m so so so excited (and a bit nervous) about tackling Maxwell and Heaviside in depth.
My favorite AM/FM Radio recipe. Delicious and tender variable capacitors and IF inductors that fall right off the ferrite core. I like just a little bit of vinegar-based sauce, some dipole slaw. Classic Carolina ham.
A Faraday cage will shield whatever is inside of it from electrical field but not from magnetic fields unless it is made out of special materials such as mu metal. CRTs were particularly sensitive to magnetic fields which distorts their image. I had one case where 10 milligauss caused problems with several. I had special enclosures made for them by a company called Amuneal at $1000 each about 30 years ago. Coaxial and triaxial shielded cables are exams of Faraday cages. For extra shielding thick ethernet backbone cable was quad shielded. 2 braids and 2 foils.
Kathy: your work is absolutely wonderful. Thank you again and again. raphael nyc
Great presentation 👏.
Thanks for sharing.
Best regards from the UK 🇬🇧
John.
Thank you, Kathy! Awesome info! Great job!
the Faraday cage we used in an electrophysics lab consisted of an inside layer of copper screen surrounded by an outside layer of the screen and both layers were separated by a wood frame. There was only one point of electrical contact maintained between the two. This formed a room for holding the electronic test and monitoring equipment so people could work inside that room while running the tests. The reason for the two layers was that a signal on the outside (like an eddy current) would generate a canceling field by the inside layer.
Your video is a wonderful and interesting overview of the Faraday cage history. Those early scientific investigators should be celebrated and studied in high school courses, in depth. Thank you and be well.
I love Kathy!
Back about 40 years ago I worked for Magnavox. I worked inside a really nice all copper Fairday cage where I would tune AM and FM stereos
Ooh, was that before or around the time that the line between Philips and Magnavox got a little hazy? I know they put both names on many products for a good while.
What a wonderful presentation! Thank you!
Very nicely done!
Awesome. I was really hoping you would cover this!
Glad I came across your channel!
I a m a. Physician and have seen old patients who were young engineers / physicists in the mid 50’s & 60’s..
Two concepts conveyed to me in the 1980’s stuck in my head all these years.
1) a vacuum quartz toroid contained (not filled) with a mixture of mercury, nano particles of iron, cobalt and barium, accelerated by external copper coils wound around the toroid and energized with increasing voltage, in the millions of volts would make the ferro-mercurial-cobalt barium mixture to flow faster and faster centered inside plasma ring This would after creating a corona effect around the tube, upon higher voltage & frequency were applied to the toroid, a white glow would appear as the radial velocity of the plasma reached near relativistic speeds. This field would keep expanding outside the toroid & experiment table . This would then cause the table where the experiment was being attached to lose weight and levitate. The explanation was that the “white field” would somehow “hide” M from gravity. Further speculation & experimentation led to the conclusion that the center of gravity of the object became “hidden” from gravity, therefore E= MC^2 would become E= c^2 or even c^ to infinity for that matter., while the field was present.
Your thoughts?
2) Some sailors involved in installing very large Diesel generators in the USS Eldridge in the mid 1940’s 3 sets of 3 Tesla coils installed in front, middle & back of the ship. The generators were connected to transformers “capable of generating millions of volts “ . These were made by RCA. What is hard to comprehend , not being a physicist, is that the 2 meter long secondaries of each set of coils, mounted in groups of 3 in close proximity but strangely enough in an X,Y, Z configuration. Each coil hat its own primary separate from the other 2 coils in the set.
Using the right hand rule, the fields would not reinforce each other. Also, using millions of volts in such close proximity would surely cause arching, which would certainly destroy the set it 3 coils . No arching was described during the dry run at lower voltage when the Eldridge was at port. There were also metal nets hanging from the deck of the ship over the sides that covered the entire hull . This was a continuous metallic net loosely fit around the hull.
What are your thoughts? The USS Eldridge was the ship,used in the so called “Philadelphia Experiment.”
Any comments on either odiferous the above accounts would be most welcome.
Dr. T - MD
with regards to 1) not likely. Anybody who demonstrated a connection between electric fields and manipulating gravity would be swarmed by physicists seeing a clear path to a Nobel prize. Somebody or bodies probably got taken in by a scammer.
The first sounds like the
C E R N collider.
Nice video. Looking forward to Heaviside's video. He's been overlooked.
Much has been made of Faraday cages and EMP. Many suggest that grounding the cage is essential. Others claim in their “experiments” that absolute electrical sealing is required (no holes). This tutorial seems to debunk most of that.
Most of the damage from an EMP is high frequency so it does need to be sealed completely because those have very small wavelengks. Also, if you have a huge pulse you probably do want to have it grounded because if all the charge is there on the surface it can short circuit. However, for AM/FM radio you sure don’t need it to be solid or grounded.
I talk more about this in my history and influence of the Faraday cage video as well as why I personally am less concerned about EMPs then many people are.
@@Kathy_Loves_Physics This is absolutely false, there is no reason that a grounded cage should protect better. It will aktually colect more charges than an ungrounded one in an electric field.
Grounding a faraday cage for EMP production is honestly quite trivial. And EMP is such a broad spectrum high frequency event that any grounding conductor that is more than 1/4 wavelength long will eventually add enough inductance to the system so as to make it as if it never really was grounded because the impedance of your grounding conductor increases with the length of the conductor. A lot of times hams on the upper floors of the building really struggle with RF in there radio room because they cannot get a ground connection that is short enough to be effective.
When I was new at the Fortune 100 electric utility I retired from, I worked in the radio shop. The shop had a faraday Cage about 6 feet high (I didn't have to duck) and 10x10 feet. It was copper clad plywood with two copper screen windows. As a ham radio operator for 20 years by then I was impressed we could key up a portable radio inside it and not be able to hear it outside the cage.
It wasn't grounded - there would be no point to grounding it.
Unfortunately we live in an old stone built cottage with very thick walls. I suspect there's iron ore in the stone (there are the remains of a 200 year old blast furnace in the field near our home) which makes the rooms, crude Faraday cages and which makes mobile phone and satellite signals very weak. It didn't matter 150 years ago when the cottage was built but not so today :)
John Flamsteed was born just a few miles from where we live in Derbyshire UK and the local school is named after him. When I want to measure anything electrical all I need to do is get out my digital meter - Faraday et al had no such option; that their primitive instruments worked well enough for them to derive their world changing discoveries is humbling.
Thanks. You explain clearly and enthusiastically as always.
Congrats on 100k subs!!!
Thank you, very nice conjunction between physics and history!
Great video
This is the best science show I have ever seen. the hertz and the size of a hole. this is great. I hope I can remember all of it.
Thanks so much. I I hope you remember all of it too 😊
This video was fantastic thankyou!
Hello kathy! I love to watch your videos. I'm requesting you to please make some videos on some renowned chemists and their work in chemistry
I occasionally talk about different chemists (Humphrey Davy, Robert Bunsen, Fritz Haber, etc) but usually only because of their influence on the history of physics because I’m a physicist and that is my area of expertise/interest.
Sorry to disappoint.
Kathy
Excellent Job!
Always interesting and always so well presented.
Loved this video. Instant subscription.
Thanks 😊
Thank you. Great research.
Glad you liked it
Love your page, like your haircut!
great video as always 👍😃
Thanks for sharing your expirences with All of us 👍😃
I think you've done a great job in demonstrating the physics and history behind the Faraday cage, although I can't see clearly where you've got to the fundamental reason why E inside is zero: it's because the charges move around the conducting cage until they reach the lowest energy state when they can no longer move; when E = 0 inside the cage conductor. You can then prove mathematically via Laplace's equation that any volume enclosed by this boundary condition, aka an equi-potential surface, is a sufficient condition for E = 0 inside.
April 10, 2023
Provo, Utah
FARADAY BAGS
You teach me a lot. Beside the Faraday cage there is also the Faraday bag which is useful to courts and law enforcement. Many courts such as the California Superior Court do not allow anyone to have a phone in the court room (except the attorneys) and put all phones into Faraday bags and remove them from the bags when the person leaves.
Faraday bags are also useful to law enforcement. Any time they take a phone the should turn it off and put it into a Faraday bag.This stops all communication with WiFi and cell towers.
Putting the phone in airplane mode does not stop ALL communication. Certain maintenance operations with the service provider DO take place from airplane mode.
In the recent Murdaugh trial in South Carolina. SLED (South Carolina Law Enforcement Division) had taken phone but only put them in airplane mode and while the phones were in the evidence lockers the towers communicated with them and changed some activity logs. This could have been avoided by putting them into Faraday bags.