Circuits Finally Made Sense When I Saw This One Diagram - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: May 22, 2025, 04:45:43 am
content: Someone on X pointed me to this.I'll struggling to find the best meme response.He seems to think he's stumbled across the golden secret to unlocking the understanding of circuits.Well, okay, great, it's just the gravity analogy. Or use the dam analogy etc.Doesn't help you avoid Kirchhoff's to actually do calculations on the more complex stuff."Circuits Finally Made Sense When I Saw This One Diagram"

author: Analog Kid
author_rank: Super Contributor
timestamp: May 22, 2025, 05:06:43 am
content: Wellll, his explanation doesn't really work for me.But that's beside the point: the point is that it works forhim.I completely understand having mental blocks about understanding electronic principles, including basic ones, because I have those myself. Amazing, unbelievable mental blocks that stop me from "grokking" how certain circuits work.So if someone can find a way to make things more understandable for them, I say more power to them. (Or more current, or voltage, or ...)

author: EEVblog
author_rank: Unknown
timestamp: May 22, 2025, 05:40:01 am
content: Quote from: Analog Kid on May 22, 2025, 05:06:43 amIt's basically just one of the many ways to learn ohms law and the basic relationship with voltage current and resistance. It's not really "understanding circuits" as such.These also works:You can also use the overcoming instead of using gravity version:

author: ledtester
author_rank: Super Contributor
timestamp: May 22, 2025, 05:54:14 am
content: Are there good analogies when a current source is the source of power in a circuit?

author: EEVblog
author_rank: Unknown
timestamp: May 22, 2025, 06:21:27 am
content: Quote from: ledtester on May 22, 2025, 05:54:14 amYou can use the water flow analogy again.Instead of having just a tap (the resistor) that controls the rate of flow of water (current), imagine you have a fixed flow rate pump (the constant current) that wants to push through a fixed amount of water flow per second regardless of the size of the water pipe it's attached to.If you have a really fat pipe (low resistance) then the pump doesn't need much voltage in order to do it's job of pumping that constant flow of water.But if you have a skinny pipe (high resistance) then the pump needs a lot more voltage in order to push that same rate of water flow through that narrow pipe.If you hit the maximum voltage you have available before the pump is able to maintain the flow, then that's the maximum compliance voltage.

author: Brumby
author_rank: Unknown
timestamp: May 22, 2025, 06:23:12 am
content: That's exactly the option I would have presented.

author: Brumby
author_rank: Unknown
timestamp: May 22, 2025, 06:24:21 am
content: Quote from: Analog Kid on May 22, 2025, 05:06:43 amNor for me.I can't say I agree with his statement that V=IR is misleading - and I certainly would argue against it being "stupid". It seemed pretty straightforward to me.I also cringe at the statement "this is exactly what's happening from a physics perspective" when he talks about his vertical model. I'll even go so far as to say outright: "No, it's not!"I'm glad it helped him - but I'm not recommending this video to anyone.

author: EEVblog
author_rank: Unknown
timestamp: May 22, 2025, 06:44:50 am
content: Quote from: Brumby on May 22, 2025, 06:24:21 amYes, both of those statements were odd.

author: nctnico
author_rank: Super Contributor
timestamp: May 22, 2025, 10:19:00 am
content: Quote from: EEVblog on May 22, 2025, 04:45:43 amIMHO he is off-track. One of the key principles of electronics (and electricity in general) is that current flows in a circle (or loop). What goes in, must come out. Or what comes out, must have come in from somewhere.About a meme response: something along the line 'electrons are supposed to be recycled'.

author: tszaboo
author_rank: Super Contributor
timestamp: May 22, 2025, 10:32:31 am
content: I=U/R is more natural for me, and that's the one that I remember.Because it's very rare that a current source is used in a practical circuit, unless you are into niche like photonics.But the rest, IDK. I never really got into the water analogy either. And this is definitely not something I would expect a post doctorate to struggle with, this is highschool level physics stuff.

author: Nominal Animal
author_rank: Super Contributor
timestamp: May 22, 2025, 01:18:07 pm
content: To me, intuitively, current is the flow of charged particles; whereas voltage is a difference in electric field potential, specifically the amount of energy needed per unit charge to move an unit charge between those two points.As is so common in physics, the "dualism" here is that charges do not exist independent of electric fields. Whenever you have a charge, you also have an electric field surrounding it; and when you have an electric field, you have some charges lurking about.As an example, when asked by anyone what exactly "current" and "voltage" really, physically are, I might answer:Current is carried by charged particles, or electron vacancies, "holes". Each particle or "hole" has a charge that is some integer multiple of the electron charge, or about 1.602·10⁻¹⁹ Coulombs. Current is literally the flow rate of those charges, usually measured as the rate of charge passing through some surface, say a cross section.Voltage is related to the electric field surrounding each and all charges. It describes the amount of energy needed per one unit of charge to move one unit of charge from one given point to another given point. Thus, voltage is always a difference, measured between two points.For me, this way of thinking makes it very easy to understand Kirchhoff's circuit laws (and the lumped element model), voltage-controlled and current-controlled transistors, and the nature and behaviour of capacitors and resistors. For inductors, I need to add magnetic fields, the "other side of the coin" for electric fields, those two forming the actual whole: electromagnetic fields. In a direct current circuit, with voltages and currents basically constants, the electromagnetic fields are basically constant too, letting us simplify many things. When they vary, the flow rates of charges vary, and therefore also the electromagnetic fields vary, explaining the basis of e.g. transmission line model and telegrapher's equations.Things just slot together nicely without me having to switch models this way; this single intuitive model just works for me, without relying on any analogs.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: May 22, 2025, 04:41:33 pm
content: So many analogies are bad. IMO, everybody could benefit from a read of the articles here-http://amasci.com/miscon/elect.html

author: TimFox
author_rank: Super Contributor
timestamp: May 22, 2025, 05:10:20 pm
content: My problem with the model on the right (resistor connected between power tag and ground) is that it perpetuates the myth that a power node and a ground node are perfect constant-potential planes. In many cases, that is a good approximation, but it is unnecessary to compute the current through a resistor connected to a battery, forming a simple loop.

author: SiliconWizard
author_rank: Super Contributor
timestamp: May 22, 2025, 05:10:48 pm
content: Quote from: tszaboo on May 22, 2025, 10:32:31 amUh, sure.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: May 22, 2025, 07:10:14 pm
content: BTW, the best ohms law and other physics stuff is by Lisanne Waifu-

author: Bud
author_rank: Super Contributor
timestamp: May 22, 2025, 07:52:40 pm
content: Jesus Christ, that is hardcore stuff.

author: TimFox
author_rank: Super Contributor
timestamp: May 22, 2025, 08:14:43 pm
content: Kawaii! Why we useKin equations for constants or fudge factors.

author: Nominal Animal
author_rank: Super Contributor
timestamp: May 22, 2025, 09:32:16 pm
content: Quote from: TimFox on May 22, 2025, 08:14:43 pmI don't see the Instagram post, but I thought it wasΚ for Kappa, Japanese reptiloid spirits who try to steal theshirikodamaorgan, the proverbial source of all fudge factors, situated within our butts.

author: TimFox
author_rank: Super Contributor
timestamp: May 22, 2025, 09:38:57 pm
content: Yes, but "kawaii" is an adjective

author: EEVblog
author_rank: Unknown
timestamp: May 22, 2025, 11:42:36 pm
content: Quote from: nctnico on May 22, 2025, 10:19:00 amYes, it adds no value at all apart from maybe helping to remember ohms law.And it introduces a ground symbol that, if you are struggling to remember and comprehend ohms law, just adds another thing to potentially confuse you.Even Joe Average who knows absolutely nothing about electricity can understand that a battery across a light bulb circuit and that something flows in the wires to turn the light bulb on.

author: UnijunctionTransistor
author_rank: Frequent Contributor
timestamp: May 23, 2025, 12:12:08 am
content: Quote from: Nominal Animal on May 22, 2025, 09:32:16 pmThe best description of shit; that is, if I have understood your analogy correctly. A big IF

author: SiliconWizard
author_rank: Super Contributor
timestamp: May 23, 2025, 12:26:19 am
content: Quote from: EEVblog on May 22, 2025, 11:42:36 pmYes, not explicitely showing a closed circuit but introducing a ground concept that is elusive is IMO going to confuse a beginner even more.

author: Nominal Animal
author_rank: Super Contributor
timestamp: May 23, 2025, 01:19:46 am
content: I took a look at the video, andI had to stop at the one minute mark.The thing here is complete lack of intuitive understanding of the lumped-element model and how Kirchhoff's circuit lawsgelwith electromagnetic fields as examined in University physics courses. From a physics point of view,currents do not need to form circuits: any flow of charged particles is a current, as long astotal charge is conserved.For a physicist unfamiliar with electricity to understand electrical circuits, the charge conservation is the first step. This is why they are calledcircuits. There are many different ways to effectively and intuitively understand voltage and current, so I guess one of those is the second step. The third step is to understand that calculating the electric field (and voltages from the differences in potential at different points) using quantum electrodynamics is unnecessarily complicated for most use cases, and the lumped-element model and Kirchhoff's circuit laws are a more appropriate model, especially if you add telegrapher's equations for transmission lines. For antennae and transformer/coil/choke geometries you also need the magnetic field aspects of electromagnetics, but generally for the rest, we tend to use finite-element method approximations and so on."Ali the Dazzling" is focused on physics, this much is clear. He obviously prefers typical physics energy level and energy level transition charts. He has no intuitive grasp on the meaning of charge conservation, or how that directly leads toelectric circuitsinstead of electric directed graphs.In truth, all he has found is an emotional crutch to assure himself he never needed to have an intuitive grasp on that other stuff (lumped-element model, Kirchhoff's circuit laws, charge preservation, transmission line model) anyway; that his physics approach will work just fine in electronics too.Hubris and stupidity of youth, ignoring things they don't understand, and being triumphant when they find a half-working crutch around that lack of understanding.I apologise for being so harsh here, but I see younger me in him; the same kind of mistakes that I am now ashamed of being paraded as superior approaches.For example, even though I did do electronics courses and have been able to read schematics for over a quarter of a century now, I didn't really construct a validintuitiveunderstanding of the nature of voltage and current before I started designing useful circuits using both voltage-controlled and current-controlled transistors.I didn't need to. But, at some point, the dissonance grew too great, and I just had to reconcile my intuitive understanding and the math and models I was using. I was well familiar with the various analogies and could apply them, but just couldn't map it correctly to my underlying understanding of electromagnetism.(It is also why I here at EEVblog forums focus solely on theintuitive understandinginstead of exact wording and definitions. When using knowledge to solve problems, it is the intuitive understanding that gives you the initial direction. When you discover you don't understand something and go learn about it, your intuitive understanding of the whole dictates how well the new information and knowledge integrates to your existing tried-and-used knowledge. It is the bridge between theory and practice. Anyone can parrot formulae, but having even a vague grasp of what it describes, means you have at least a chance to successfully use said formulae in some useful purpose without external prompting.)I'm sure that if I thought about it for a few days, I'd find a better way to express all this. For now, assume that I am projecting my own failures on poor Ali the Dazzling. Or perhaps they're just a little bit less dazzling than they believe.

author: Nominal Animal
author_rank: Super Contributor
timestamp: May 23, 2025, 01:29:21 am
content: Quote from: UnijunctionTransistor on May 23, 2025, 12:12:08 amWell, the Japanese folklore says that shirikodama is a jewel or sphere inside your butt that somehow contains your soul, that these water-dwelling reptiloid spirits like to steal from you.In my opinion, all fudge factors are pulled out of ones butt –– or, in scientific terminology, have been generated using the Stetson-Harrison method, i.e. pulled out from your hat, with the Harrison part there to just lend credence to the term –– so me being me, I think shirikodama is just the source of brainfarts, trial-and-error fudge factors, straight up guesses you forget to mention are such, and other similar semi-shameful numerical and algebraic sleight-of-hand.And that aluminium foil hats shield one from shirikodama too. At least if you chew the foil.

author: fourfathom
author_rank: Super Contributor
timestamp: May 23, 2025, 01:57:20 am
content: Quote from: UnijunctionTransistor on May 23, 2025, 12:12:08 amReminds me of the "DRE" estimation process we used when necessary in my last company. (DirectRectalExtraction)

author: EEVblog
author_rank: Unknown
timestamp: May 23, 2025, 03:27:57 am
content: Quote from: SiliconWizard on May 23, 2025, 12:26:19 amCountless people get confused by the ground (and earth) symbols, even some some basic knowledge of circuits.This is why the battery and light bulb circuit is the universal way to teach basic electric circuits.He seems kinda upset that somehow he couldn't remember the ohms law triangle and couldn't apply it in a circuit with a battery and a resistor, so assumes everyone has that problem?

author: Ranayna
author_rank: Super Contributor
timestamp: May 23, 2025, 06:52:35 am
content: Quote from: ledtester on May 22, 2025, 05:54:14 amI had the longest trouble with the concept of constant current.I learned with analogies, actually mainly from the Kosmos Kits. That started with the water analogy up to transistors, and then went to electron flow from negative to positive. Oh boy did that get my brain in a twistEspecially once i left the world of that Kosmos kit.Though i never got any formal electronics education after that.That it is just as simple as a variable voltage took a while to click for me.

author: Nominal Animal
author_rank: Super Contributor
timestamp: May 24, 2025, 04:22:14 am
content: Quote from: EEVblog on May 23, 2025, 03:27:57 amI only remember \$U = R I\$ because of Uri Geller 🤮. Easy enough to divide by \$I\$ to get \$R = I / U\$, or by \$R\$ to get \$I = U / R\$.

author: pcprogrammer
author_rank: Super Contributor
timestamp: May 24, 2025, 06:32:11 am
content: Quote from: Nominal Animal on May 24, 2025, 04:22:14 amThe only thing to remember is that Ohm's law exists. The internet quickly supplies the formulas. Knowing how to use them and understand the results, is another issue.The elevated ball analogy in the video is kind of bullshit. There is only the air resistance limiting the speed, and when it reaches the ground it will bounce. Adding a tube to create more resistance only goes so far, depending on how malleable the ball is.

author: Nominal Animal
author_rank: Super Contributor
timestamp: May 24, 2025, 08:51:35 am
content: Quote from: pcprogrammer on May 24, 2025, 06:32:11 amTrue enough. I started my Uni studies in mid-nineties (that includes the college part for USians), so I kinda-sorta had to memorize some. That's one that stuck. (Probably because U. G. was always a charlatan "psychic" and spoon-bender, and only in the last two decades or so has tried to rewrite his history as him being an "illusionist and magician". That kind of fakery and history-rewriting has always made me 🤮.)For Kirchhoff's circuit laws, I never remember which is which anyway. Same with Maxwell–Heaviside and most others. I do remember \$\mathbf{F} = m \mathbf{a} = d \mathbf{p} / d t\$, but not which Newton's law of motion it is, because I worked with simulator code integrating particle paths with variable-length time steps.Quote from: pcprogrammer on May 24, 2025, 06:32:11 amThat's exactly what my rants aboutintuitive understandingare based on. Get that part right, and you don't need to memorize any names or equations, just have a grasp of the basics, and good DuckDuckGo-fu to search stuff efficiently.

author: EEVblog
author_rank: Unknown
timestamp: May 24, 2025, 09:57:50 am
content: Quote from: Nominal Animal on May 24, 2025, 04:22:14 amSagan had trouble remembering the ohms law triangle. I told him to imagine the pyramid from Stargate and the V on top is an upside down version of the home world symbol.The I and R can go in either order on the bottom, it doesn't matter.He thought that was awsome and doesn't forget it now.

author: EEVblog
author_rank: Unknown
timestamp: May 24, 2025, 10:00:05 am
content: Quote from: pcprogrammer on May 24, 2025, 06:32:11 amI think his vertial analogy isn't really about the ball, it's about visually remembering that the voltage V is on the top, just like it is on the ohms law triangle.That's it, that's th whole thing, the V is always on the top.I=V/RR=V/I

author: temperance
author_rank: Super Contributor
timestamp: May 24, 2025, 10:15:57 am
content: QuoteI've encountered quite a few engineers who obtained an engineering degree because they can memorize the stuff they have to learn without understanding anything of it. On the job they are clueless because they don't know how to work with the "facts" they acquired. They simply don't see how things are connected.My memory, on the other hand, is a sieve for raw facts. I have long experienced that as a giant obstacle and in school you are being punished twice a year for not being able to just memorize raw facts. Only much later I understood the value of being able to truly understand something. Sure, I don't remember tables of integrals and laplace transforms like some do. I have to look them up if I need them.Maybe it is a rude thing to say. But people extremely good at memorizing raw facts are often incapable of thinking.

author: tggzzz
author_rank: Super Contributor
timestamp: May 24, 2025, 10:20:25 am
content: Quote from: EEVblog on May 24, 2025, 10:00:05 amHaving to remember that kind of visual analogy makes me wonder how proficient people are with basic algebra (which ismuchmore important than a single formula!).What's so difficult about remembering V=IR, and from thatmentallyworking out the others?Ditto s=vt, c=fλ, etc.

author: temperance
author_rank: Super Contributor
timestamp: May 24, 2025, 10:33:38 am
content: QuoteSome people can be extremely proficient at algebra but incapable of understanding how to apply algebra in the real world.

author: EEVblog
author_rank: Unknown
timestamp: May 24, 2025, 10:51:38 am
content: Quote from: temperance on May 24, 2025, 10:15:57 amIn my experience that seems to be the rule rather than the exception.

author: pcprogrammer
author_rank: Super Contributor
timestamp: May 24, 2025, 10:54:56 am
content: Quote from: EEVblog on May 24, 2025, 10:00:05 amAh yes, missionary style.Still his explanation in that video about the analogy, where what is stopping the ball is the resistance, all nice and dandy, but the physics for the two are different. A bucket of water and a pipe would be better as an analogy for sure.And what if there are multiple voltage sources, or a mix of voltage and current sources, it won't be so easy to use his system to simplify things. But if it works for him and others, more power to them. I will stick to my own understanding of things.

author: nctnico
author_rank: Super Contributor
timestamp: May 24, 2025, 11:01:30 am
content: Quote from: EEVblog on May 24, 2025, 09:57:50 amIf you are oriented to remember visual things (photographic memory), then using the triangles is a good way to remember these simple formulas. Just recall the triangle image and you know the formula.

author: tggzzz
author_rank: Super Contributor
timestamp: May 24, 2025, 11:07:18 am
content: Quote from: EEVblog on May 24, 2025, 10:51:38 amMy experience is exactly the opposite: I usually see people who have a shallow surface levelunderstandingappreciation of a topic, and are unable to see the underlying unifying fundamentals.That's especially true with software, but also applies to electronics.

author: tggzzz
author_rank: Super Contributor
timestamp: May 24, 2025, 11:16:25 am
content: Quote from: nctnico on May 24, 2025, 11:01:30 amYes and no.I remember relationships rather than isolated facts. That makes spatial diagrams easy, but names and foreign language vocabulary difficult for me. For example it seems I, probably when I was <9 years old, invented an internal ribbon-like visualisation of numbers that makes mental arithmetic easier (for some number ranges and precisions).How many times have you seen schematics where the components and signal flow are arbitrary to the point of being bizarre? I'll bet the perpetrators don't have a good understanding of the fundamentals, and are doing monkey-see-monkey-do engineering.

author: temperance
author_rank: Super Contributor
timestamp: May 24, 2025, 11:18:01 am
content: QuoteIsn't that what being stated? People who can cite each and every formula and rule without understanding what it means, where it came from and how it applies in the real world?

author: Sorama
author_rank: Frequent Contributor
timestamp: May 24, 2025, 11:24:14 am
content: I’m kind of surprised to read that some people are having difficulties in understanding this.Does this imply those people have no formal education on electricity ?Are there EE not understanding this very basic electrical principle?

author: tggzzz
author_rank: Super Contributor
timestamp: May 24, 2025, 11:39:39 am
content: Quote from: temperance on May 24, 2025, 11:18:01 amNoA couple of quick simple examples...Electronics: thinking there is a 0V or "ground" or "earth", or that digital == binary, or that to characterise a 200ps risetime a scope needs to sample >>1GS/s, or that to digitise an X Hz signal a scope only has to sampling at >5X S/s.Software: thinking that a distributed system can ever guarantee ACID properties, or that there is a shared global time. (For those that doubt those, please solve the Byzantine generals problem and improve on Leslie Lamport's temporal logics. Succeed, and you will be famous)

author: tggzzz
author_rank: Super Contributor
timestamp: May 24, 2025, 12:25:52 pm
content: Quote from: Sorama on May 24, 2025, 11:24:14 amToo often that does happen. It is often associated with people who make statements like "schooled in the university of life", or "practical experience is more important that theoretical knowledge", or "I know a PhD student who attempted to measure the impedance of the mains supply with an Avo8 meter".There is - and should be - a fundamental difference between a technician and an engineer. The medical equivalent is doctors and nurses, and nurses can be dismissive of doctor's abilities.For the avoidance of doubt, neither is better than the other; they have complementary skills. There is also overlap.If I want good soldering or a wound closed, then I want a nurse/technician rather than a doctor/engineer.If I want a system designed or a disease diagnosed, then I want an engineer/doctor rather than a nurse/technician.

author: temperance
author_rank: Super Contributor
timestamp: May 24, 2025, 01:09:34 pm
content: QuoteThere is the difference between those who are good at what they do and understand the underlying fundamentals and those who fail who will never understand the underlying fundamental although they have the same qualification. I'm sure you don't want the latter to come and diagnose whichever problem you have.

author: amyk
author_rank: Super Contributor
timestamp: May 26, 2025, 03:27:39 am
content: I don't think I actually memorised the Ohm's Law equation as-is for much of my early years in studying and work, as it seemed "obvious" from the water analogy that given a fixed resistance, increasing voltage will proportionally increase current, and for a fixed voltage, decreasing resistance increases current, inversely proportional.Likewise, I've always found explanations of inductance with phrases like "this end of the inductor becomes positive" to be very confusing, but it's much simpler to think of it as inertia attempting to continue the current flowing in the same direction it was before.

author: radiolistener
author_rank: Super Contributor
timestamp: May 26, 2025, 09:25:16 am
content: If voltage is gravity, I’m curious - what’s the gravitational analogy for a short circuit? A black hole where electrons go to die?

author: TimFox
author_rank: Super Contributor
timestamp: May 26, 2025, 02:27:29 pm
content: Quote from: amyk on May 26, 2025, 03:27:39 amThe inductance attempts to continue the current by inducing that positive voltage when the current changes.V= -LdI/dtwhere you need to be careful about signs.

author: tszaboo
author_rank: Super Contributor
timestamp: May 26, 2025, 03:32:25 pm
content: Quote from: amyk on May 26, 2025, 03:27:39 amI had this assistant professor, who was telling me that you don't need to remember Ohm's law, because its just an edge case for Maxwell's E = ρJ, so just remember all the 8 (+Bonus depending on who you ask) Maxwell's. Because you need to remember those anyway.I think he was actually serious about it.

author: TimFox
author_rank: Super Contributor
timestamp: May 26, 2025, 03:52:53 pm
content: Quote from: tszaboo on May 26, 2025, 03:32:25 pmIn that equation,EandJare vectors, so it is easier to keep track of polarity and direction.In both formulations, the physical content is that the resistivity (or conductivity) in the vector form, or the resistance (or conductance) in the scalar form, is constant. This defines “ohmic” materials, which are linear in this context, for which Ohm’s Law is appropriate, but not all materials or devices are ohmic.

author: tszaboo
author_rank: Super Contributor
timestamp: May 26, 2025, 04:31:42 pm
content: Quote from: TimFox on May 26, 2025, 03:52:53 pmEvery single one of the Electromagnetic fields equations come with a whole list of ifs and buts. And a disclaimer, that sigma in this one is different than the sigma in the other equations .I find them ultimately unpractical to use, and an entire department in 2 semesters couldn't give one challenge which wasn't something like:"There is a spherical cow floating in space, above an infinitely large sheet of metal, and on an infinitely tiny wire 10A constant current is flowing into the cow. What's the voltage or whatever?"And this came from the people who were basically saying that every other department is "just" using a somehow bastardized version of the Holy Maxwell.While even writing down, not even solving the boundary conditions is a serious undertaking.

author: SiliconWizard
author_rank: Super Contributor
timestamp: May 26, 2025, 04:33:14 pm
content: Quote from: EEVblog on May 24, 2025, 10:51:38 amYes, it seems rather common.For the record, "intelligence", which has quite a few definitions, comes from the latin word "intelligere", which ultimately means "interconnecting" things.

author: TimFox
author_rank: Super Contributor
timestamp: May 26, 2025, 04:48:55 pm
content: Quote from: tszaboo on May 26, 2025, 04:31:42 pmYeah, sometimes the conductivity (sigma) or resistivity (rho) is a tensor, not a scalar, in solid materials (some of which resemble lasagna).In that case,JandEvectors are not in the same direction.This is important in solid-state physics, which often produces useful components.