7 ms·
What Is Electricity? (2013)
- dang 7y agoA thread from 2015: https://news.ycombinator.com/item?id=10400123 https://news.ycombinator.com/item?id=10400123
- javajosh 7y agoOne aspect of electricity I think is useful to emphasize is that electrons in a conductor move more like the steel balls Newton's cradle (that toy you may have seen where a ball strikes one end of a line of balls, and nothing moves except the end ball, or you can pull back two balls and then only two balls will move, and so on). This can help with intuition about the distinction between "holes" and electrons, and how energy can flow with holes (which is quite counter-intuitive, I think). In terms of mental model, the ratio of holes to ambient electrons is sometimes useful to think about, as this is fundamental to computing current limits of conductors. There is a diagram (an animated GIF) about half-way down that sort of implies the newton's cradle method of moving charge, but I don't like it because it's not clear enough. Also, I see current as more of a fixed cloud of valence electrons with holes moving through it - which is a very different intuition than what this diagram implies.
- Koshkin 7y agoLooks like what you are describing is a model of the conductivity in the valence band (of a semiconductor). In the conduction band of a metal electrons move freely, their forward mobility being impeded only by heat.
- javajosh 7y agoWell, maybe the part about the holes. But even wikipedia mentions newton's cradle! https://en.wikipedia.org/wiki/Electrical_resistivity_and_conductivity#In_metals https://en.wikipedia.org/wiki/Electrical_resistivity_and_con...
- nixpulvis 7y agoThe distinction is between the speed of propagation (e.g. how fast between a light switch flipping until lighting the room) and the physical movement of subatomic particles through the wire. https://en.m.wikipedia.org/wiki/Drift_velocity https://en.m.wikipedia.org/wiki/Drift_velocity
- lilgreenland 7y agoHere's my take on a cartoony conductivity simulation. I've got three models: conductors, semiconductors, and semiconductors but with holes. https://landgreen.github.io/physics/notes/electromagnetism/charge/index.html#conductivity https://landgreen.github.io/physics/notes/electromagnetism/c...
- dreamcompiler 7y agoI like these diagrams. Now I want to see what superconductivity looks like in your framework. An unimpeded stream of electrons flowing as if the red dots aren't even there?
- lilgreenland 7y agoMy simulation just runs classical physics (Coulomb's law + Newton's laws). It's missing any mechanism for super conductivity. Although, I could just turn off friction. I think superconductivity means the electrons pair up and stop colliding through the Pauli exclusion principle. I didn't code any collisions, so maybe it's already modeling a crappy version of superconductivity!
- javajosh 7y agoYes, that looks much closer to what I have in mind, although I also tend to think of electrons as not visible individually and doing this as part of a large cloud over a 3-D crystalline substrate.
- lilgreenland 7y agoI teach high school physics. Here's my notes/textbook on electricity with simulations and equations rendered in LaTex. https://landgreen.github.io/physics/notes/circuits/electricity/index.html https://landgreen.github.io/physics/notes/circuits/electrici...
- new4thaccount 7y agoI haven't gone through all of your notes yet, but this would've been a godsend to go over in highschool before I started my EE classes in college. It was always obvious which students had been lucky enough to already cover the material.
- jaequery 7y agoThis is amazing ! Really well put together!
- montecarl 7y agoAwesome notes. I haven't had my coffee yet so perhaps I'm just misreading this part: "In 1746 Benjamin Franklin mistakenly assigned a negative value to the charge carriers that we now call electrons." Shouldn't that read "mistakenly assigned a _positive_ value to the charge carriers that we now call electrons"?
- lilgreenland 7y agoNope! It's kinda silly. We all call electrons negative because of how they were labeled 250 years ago. If he had labeled them positive the math involving electric current would be a bit easier. https://xkcd.com/567/ https://xkcd.com/567/
- negamax 7y agoJust amazing! Imagine all the physics and knowledge from multiple sciences, disciplines and fields are used when someone tells Amazon Echo to turn on a charger or socket that’s connected to a phone or laptop. Echo -> ISP wires —> Undersea Cables —> Amazon Servers -> Back home -> Electricity flow And this is so super high level All of these devices on the way are powered by electricity from dams, solar, wind etc. Before voice to speech hits or data is read. Processors and hard disks must do so much heavy lifting It’s surreal the level of abstraction we are surrounded by..
- aaronblohowiak 7y agoQuite fascinating and mind-boggling. What really blows my mind is that technology is still extraordinarily less complicated than (bi|ec)ology.
- geggam 7y agoIt's interesting to me when I read it. We take it down to the proton neutron and electron stating they are charged with positive negative or neutral charge.... but what are they charged with ? Electricity ? What is it made of ?
- dreamcompiler 7y agoIt's made of the electromagnetic force. We can measure it and characterize it very accurately with mathematics. We can say what it isn't (gravity or the weak force or the strong force), but we cannot say what the electromagnetic force is. Sorry. If you figure it out you'll get a Nobel Prize.
- rnestler 7y ago> We can say what it isn't (gravity or the weak force or the strong force) Isn't the electric and the weak force considered the same force these days? See also https://en.m.wikipedia.org/wiki/Electroweak_interaction https://en.m.wikipedia.org/wiki/Electroweak_interaction
- tntn 7y agoThey aren't "charged with" anything. Some elementary particles happen to interact with one another in a particular and consistent way, and we label them according to how they behave with something we call charge. Electric charge is fundamental.
- Koshkin 7y agoWe say that a macroscopic body is “electrically charged” when there is an excess (or a lack) of electrons in it - which merely creates a disbalance between the electrons and the protons. We say that an elementary particle is electrically charged to indicate that there is a nonzero probability of it emitting or absorbing a photon (which leads to creation of the electromagnetic force).
- deleted 7y ago[deleted]
- asark 7y ago
- williesleg 7y agoWait, what????? Generators don't generate electricity from nothing????? It's all been a scam????? Say it ain't so!
- carapace 7y agoFor an exercise in clear (and perhaps provocative) thinking, try: 'What Is "Electricity"?' ©1996 William J. Beaty > What is electricity? This question is impossible to answer because the word "Electricity" has several contradictory meanings. These different meanings are incompatible, and the contradictions confuse everyone. If you don't understand electricity, you're not alone. Even teachers, engineers, and scientists have a hard time grasping the concept. > Obviously "electricity" cannot be several different things at the same time. Unfortunately we've defined the word Electricity in a crazy way. Because the word lacks one distinct meaning, we can never pin down the nature of electricity. In the end we're forced to declare that there's no such stuff as "electricity" at all! http://amasci.com/miscon/whatis.html http://amasci.com/miscon/whatis.html
- Koshkin 7y agoAnalyzing the meaning of words is characteristic to philosophy and is not a sign of “clear thinking.”
- HNLurker2 7y agoThis is trivial for somebody who studies electrical engineering in highschool
- kalado 7y agoBasic introductions of a topic are trivial for people that are studying that topic? Shocking!