Confused about electricity after watching Veritasium video - Page 1
Forum section: electronics / beginners

author: pndv
author_rank: Newbie
timestamp: August 30, 2022, 09:42:14 pm
content: For reference, I am talking about this video:And EEVBlog response:Also, I am a software engineer, and not elecrtrical or electronics engineer so please don't hate me for my stupidity. And now my question:If the the flow of current and the subsequent magnetic field is the reason for light speed travel, then1. How does the current flow work? Is it the electrons, or electro-magnetic radiation? What is it that is carrying the energy?2. If it is not the electrons but electro-magnetic fields, then why are the lines running on PCB do not affect different lines which run so close to each other?3. Why do we need insulation? Can plastic/non-conductor block these radiations? I mean the definition of conduction is that it requires a medium to flow whereas radiation, by defintion, flows without medium.4. If the electro-magnetic field itself is causing the energy flow then why do we need to connect the wire to negative? Whatever is "flowing" will take long time to reach the negative terminal.5. Consider the hypothetical scenario in this crude diagram, and tell me how long will it take for the bulb to turn on:----- 3 light-second long wire ----- (+ battery - ) ----- 3 light-second long wire -----| || || |3 light-second long wire 3 light-second long wire| || || |----- 3 light-second long wire ----- ( bulb ) ----- 3 light-second long wire -----

author: ataradov
author_rank: Super Contributor
timestamp: August 30, 2022, 09:57:20 pm
content: There is already a million page thread on thishttps://www.eevblog.com/forum/chat/veritasium-(yt)-the-big-misconception-about-electricity/We really don't need another one.

author: thm_w
author_rank: Super Contributor
timestamp: August 30, 2022, 10:17:10 pm
content: Just ignore the Veritasium video, pretend you never saw it, and find some electronics fundamentals to study instead.

author: Sredni
author_rank: Frequent Contributor
timestamp: August 30, 2022, 10:18:12 pm
content: For some reason I feel like Roger Rabbit, in that bar...Anyway, this topic has been discussed in very long threads on this forum - I believe in General Technical Chat - and you might want to read those 50-80 pages threads to get a full spectrum of possible interpretations.I'll give you mine here in its 'short' form.Charges are associated with an electric field, charges in motion are associated with an additional magnetic field. Changes in the configuration (of position, speed, acceleration) of the charges propagate at the speed of light from the charge themselves, in the surrounding space.When the switch is open, charges of opposite sign are accumulated at the switch's terminal - they are on the surfaces of the conductors the terminals is made of - and in part on the surface of the remaining conductors in the circuit (whatever is needed to have a net electric field equal to zero inside the conductor). When you flip the switch, the surface charge distribution start to change - some charge recombine, some surface charges move, some inner charges start to move. With this change in configuration, comes a change in the electric and magnetic fields that propagates at the speed of light in the medium.You have two phenomena going on: the redistribution of surface charge along the conductor starting from the switch, and the perturbation in the field in the whole of space around the disturbed region. The first phenomenon will travel along the wires and will take a lot of time to complete when the wires are very long (even tho it is very fast in itself - just a fraction of the speed of light); the second phenomenon does not need wires and will travel through space and the insulating material at the speed of light (in the medium it is going through). This latter perturbation in the fields will start to change the distribution of charge in the conductors it encounter along its path, even if they have yet to be reached by the 'wired' perturbation.This is the effect Veritasium sees at time 1/c, well before the perturbation on the wire reaches the lamp. It is an incomplete configuration of surface charge, that will be short lived unless the reinforcement will come from the perturbation of charge traveling along the wires.Where is the energy traveling? This is debatable.My view is that we put energy in the fields (or rather in the system of charges that produce them) by perturbing them, the perturbation travels at the speed of light and then we can extract energy from whatever portion of space has the right configuration of fields.For example, by closing the switch we perturb the system in such a way that there will be an accumulation of charges of opposing sign at the resistor - conductor interfaces. These opposing charges will create a strong electric field inside the resistor, that will greatly accelerate the free electron, locally giving them a lot of energy that they will lose to the lattice, producing heat. The electrons did not have that energy before entering the high field region of the resistor, and they will not have it after leaving it. It's locally acquired, thanks to the EM fields that mantain that charge imbalance.But for the EM fields to be that way, you need the conductors to host surface charge. That's why you need wires to 'transfer' large amount of energy.

author: pndv
author_rank: Newbie
timestamp: August 30, 2022, 10:52:19 pm
content: I am very sorry for the repost, I searched the entire forum with `Veritasium` and got only 2 results which were links to his channel. Please close this thread.

author: pndv
author_rank: Newbie
timestamp: August 31, 2022, 02:11:41 am
content: How about the hypothetical question I posted, how long will it take to turn on the light bulb?

author: IanB
author_rank: Super Contributor
timestamp: August 31, 2022, 02:47:00 am
content: Quote from: pndv on August 31, 2022, 02:11:41 amThere is no simple answer to that question. The bulb does not instantly go from "off" to "on", so you will have to define what you mean by "on"?In short, any answer that does justice to the question will be too complex to understand without a lot of prior grounding in physics.

author: MrAl
author_rank: Super Contributor
timestamp: August 31, 2022, 07:49:56 am
content: Quote from: pndv on August 30, 2022, 09:42:14 pmHello,There is a lot to this but there is interaction between wires or circuit traces. One way we can look at this is by using the concept of mutual inductance. Two wires then interact in a way similar to a transformer and if you model it as a transformer you have three inductances and the mutual inductance is what is thought of as being between the two wires just like a transformer would have.The derivation is rather involved, but you can start with the Law of Biot Savart for static fields and derive a formula for two parallel wires, then calculate the mutual inductance. The integrations required for two parallel wires is not too difficult but for anything else it can get kind of hard to calculate.One of the ideas in classical theory is that both the field and the electron movement occur simultaneously. That means that at the very instant that the field starts the electrons start to move.Now one way to derive the field is by using small masses coupled by small springs. As you let the masses becomes smaller and springs shorter, you start to see the field propagate as the number of masses becomes infinite and the masses become massless, thus we see light. However, it may be that because the masses are small but not infinitesimally small, there is probably some spring action left which means as the field propagates down the wire the electrons in the local vicinity move instantly but the ones farther down the line take a tiny bit longer because the field hasnt reached that point yet.If you really want understand more about this i would suggest starting with the Law of Biot Savart and take it from there. That starts you off with a static field. You can then move maybe to the Feynman derivation for dynamic fields. In any case you will need to integrate a lot and there will be some difficult integrations to perform.It is interesting how this all works though and what we take for granted.

author: RubyRhod
author_rank: Contributor
timestamp: September 01, 2022, 09:30:39 am
content: Quote from: pndv on August 31, 2022, 02:11:41 amThe lights are already on. The switch you throw merely turns your eyes on.

author: JohanH
author_rank: Frequent Contributor
timestamp: September 01, 2022, 09:52:45 am
content: There are many answers on many levels. The simplest is that for a DC circuit you don't have to bother much. When taking transients into account, you already have to bother somewhat. And with high-speed digital signals, all the time. One key concept is transmission lines. Look it up.Quote from: pndv on August 30, 2022, 09:42:14 pmIn DC circuits, we imagine it's the electrons, because it's enough for Kirchhoff's law.Quote from: pndv on August 30, 2022, 09:42:14 pmAt low frequencies and DC, they don't affect each other much, but at high frequencies they do more. In high-speed design, you definitely have to take this into account.Quote from: pndv on August 30, 2022, 09:42:14 pmIn a DC circuit (or AC circuit at low frequencies) we don't usually have to bother with the radiation, because it's so small. There insulation is about keeping voltages isolated. Radiation is usually about very small voltages.Quote from: pndv on August 30, 2022, 09:42:14 pmYou still have to have some electrical circuit to create the electromagnetic waves in the first place. You can't create radio waves in air from nothing.Quote from: pndv on August 30, 2022, 09:42:14 pmAs you have drawn it, it won't work as the Veritasium circuit, because there is too great distance between the wires to create any meaningful electrical field between the wires. So it will behave like a common DC circuit.

author: Terry Bites
author_rank: Super Contributor
timestamp: September 05, 2022, 11:54:14 am
content: Don't be. See Vs defence video clearing some misconceptions.I recall Mehdi Boom explains why current carrying wires are nor filled with moving balls.It’s interesting and quite correct. The flow of current is an EM phenomenon, not loads of elections barrelling down wires.Mostly we are shown models that just help us visualise flow of current as fluid or balls.Current is defined as charge (Coulombs) per unit time not the number of electrons (Moles) moving per unit time. Elemental charge is denoted as "e", that's not the same thing as the particle named e. The fact that an e carries e coulombs really doesnt help clear that up. None of this is controversial.Still, some people find this idea deeply upsetting and refer you back to historical misconceptions about electricity. Usually from over 100 years ago. “The world is flat and I’ll show you a flat earth map to prove it”!So much for the physics.For (most) electrical engineering purposes, you can visualise it as water or balls- whatever works for you is fine. Don't lose sleep over it.

author: Psi
author_rank: Super Contributor
timestamp: September 05, 2022, 12:03:59 pm
content: Yep, electricity creates magnetism and magnetism creates electricity.The key to the veritasium video is that the parallel wires are so close together.