hi we all know that as we age our skin starts getting stretchy and Droopy in many places but it is a proven scientific and medical fact that if you apply high enough voltage across your loose skin you will die yes I'll be talking about the skin effect but the electrical skin effect has nothing to do with the live skin all it's about is that when we run AC current through a conductor the magnetic fields inside the conductor push the flow of current towards the surface or the skin of the conductor does it mean those fields
push charges to the surface of the conductor to flow if so I can show it easily same as how my sponsor brilliant easily shows simple to complex Concepts through their interactive lessons there is no regret in signing up through my link brilliant.org electroboom you get full 30 days free to try brilliant and learn as much as you can but most importantly you actually learn to program to science to analyze data and more at the end to show how charges go to the surface I have two wires running side by side and I will run current
in the same direction in both with my power supply and we can see these wires separate apart as we turn on the supply see oh sh middle finger is for B field well yes middle finger according to the right hand rule for same direction currents the force on wires is towards each other they repel each other when the currents run in opposites I already knew it too that's the whole reason for lightning say when charges start flowing from clouds to the ground the magnetic fields pull them together and eventually create a single Channel now this
confuses me for two reasons first problem I have is we had a debate with veritasium a while back where we agreed how spread of charges in a wire is uniform and now this suggesting magnetic fields should pull charges towards the center of the wire and second problem is well in skin effect the charges should flow at the outer skin layer of the conductor not at the center my test was DC though it might be something AC does I'm going to run AC current through my WI I need to limit the current through the wires of
course using my auto Transformer same direction AC current through the wires let's see for the lav of F and the wires got attracted together and melted shot and so we read Wikipedia the magnetic fields generate any currents that oppose the flow in the middle oh oh hi I'm an expert in skin effect now well before explaining skin effect let's talk about my experiments of attracting wires versus the flow of charges remaining uniform inside the wire rather than accumulating in the middle according to Lauren's Force law there are two types of forces affecting moving charges electric
and magnetic forces in a wire though or especially in short distances electric force is typically the dominant force between the two significantly larger than the magnetic force so in a wire between magnetic fields pushing charges to the middle and charges wanting to return back to their positions to create electric equilibrium of course electric force wins magnetic force is in no way strong enough to create such a charg im balance in a wire but it's there so in my opinion it might create an incredibly small charging balance inside the wire we can ignore I'll park that
thought for now let me know if there is an article on the in the comments the reason the two wires jump at each other though is because to simplify ignoring the small effect of Relativity of objects in motion there is no charge IM balance or electric force because electrons and protons move together in the wire structure there is only an attracting magnetic force which is due to the relativity of objects in motion now to skin effect it's not about charges moving to the surface of a conductor it's about the electric current not flowing in the
middle the charge distribution is still in equilibrium in The Wire this can only happen in AC though the reason is that only alternating current creates changing magnetic fields that inside the wire induce Edie currents I have explained Eddie current back in my old video you can watch for more details but basically when AC current flows one way in the wire in a snapshot of time creating magnetic fields in a certain direction the resulting Eddie currents are always such that they amplify the surface currents but oppose the center currents so less current in the middle I
think there's a way for me to show that the current is lower in the middle of The Wire by making a wire with multiple strands I have seven short strands of wire and I'll Place one of them in the center and the rest around it like this I soldered all of them together on one side but on the other side I separated the center one from the rest of the six see according to the skin effect equation the skin depth which is a depth in The Wire skin where over 60% of the current runs through
reduces as the frequency Rises like in Copper it is 8.4 mm at 60 HZ but 0.2 mm at 100 KZ so I'm thinking with my arrangement of wires the center wire current should stop as frequency Rises now to measure the current well that was a waste of time experiment I'm an idiot but remember those Edie currents I cut right through them by using multiple strands killing them this is one of a good ways to reduce skin effect in my measurements the center and outer currents remain closed until frequency rises above 10 MHz after which it
enters the realm of black magic how can I measure it then okay here's my next scheme to avoid cutting the Edie currents I'm using a wide copper tape then inject AC current one way and pulling it out from the center and outer layers separately to measure another pointless effort so as I measured the middle current actually drops but only when I get to 5 MHz after which it is black magic again middle current should drop way more significantly at much lower frequencies yes it may work to some extent but remember a wire is a three-dimensional
cylinder and all the Eddie currents concentrate in the middle having a much greater impact than my flat two-dimensional copper okay here's another idea skin effect literally increases the resistance of the wire no I'm not talking about the impedance due to inductance but the actual resistance because the current rather than flowing through the entire crosssection of the wire flows through a thin skin to measure the resistance I typically run a bunch of current Through the Wire and measure the voltage across it and that gives me the resistance but in AC wire also has inductance so the
voltage across it is a result of both resistance and inductance which is a problem okay I have an idea I run an AC current through a rod as my wire and I can check the current by measuring voltage across a 1 ohm resistor then I measure the voltage across the rod like this mess of a setup here's my rod with the probe wires across it measuring the voltage which is the blue Trace down there which is just a few Mill volts and the yellow Trace is the current through the rod that has a 1 amp
Peak now you'll see that uh if I have the probe wires wide and open like this I read a higher voltage compared to if I bring the wires tightly close to the rod reason is in the loop consisting of the rod and my probe setup where current only flows through the rod and nothing through the probe wires if magnetic fields generated by the rod mostly go through the loop the voltage we read at the scope is the sum of the voltages across the inductance and resistance of the rod but if we run the probe wires
tightly close to the rod then twist them back to the scope making sure the magnetic fields mostly wrap around the probe wires to we mostly only read the voltage across the resistance of the rod why because now the probe wire inductance and Rod inductance are coupled together like a one toone Transformer the coupling is not 100% % but ideally the same voltage that falls across the rod induct H is also coupled on the probe wire and so we only read the resistor voltage beautiful plan here I tied the probe wires very closely to the rod
so here at 1 khz I'm running a 1 amp Peak current through the rod and I'm reading a voltage across it which is only like half a molt which means the resistance of the rod is only half a milliohm now let's raise the frequency the current remains around the same maybe a bit less but you see as I'm raising the frequency the voltage is getting bigger and bigger so although the current is a bit lower the peach voltage across the rod is almost double at around 35 khz so clearly the rod resistance has increased skin
effect I finally measured it what's the use of the skin effect well nothing really it just makes for worse resistance and wastes more power you would think making a thicker wire would help but really you adding a ton of copper in the middle that current doesn't run through anyway that's why in high power lines they can happily trade the wire core with a steel wire to make a much stronger wire that can hang over long distances without breaking or in induction heaters they actually use a copper pipe without affecting the coil resistance but now they
can run water through it to keep it cool but I have to make an apology in my early days of learning about skin effect I thought that's what saves humans when they are exposed to high voltage high frequency signals I thought skin effect makes the current run only on the body surface not hurting your organs why doesn't it hurt well that's not the case skin effect is very dependent on the conductor resistance you know changing magnetic fields create an electromotive force or voltage inside the conductor that divided by the conductor resistance defines the amplitude of
the Edie currents so the higher the resistance the lower the Edie Curren and the less the skin effect so inside the human body that has a resistivity of like a million times more than copper there is barely any Ed currents and the actual High current can travel deep inside your body the reason you don't get shocked and die is because your nerves don't react to frequencies over say 30 khz anymore so your muscles won't freeze but the high frequency High current cooks and burns you over time so it's not an immediate death you get to
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