What is Skin effect: Definition and 41 Discussions

Skin effect is the tendency of an alternating electric current (AC) to become distributed within a conductor such that the current density is largest near the surface of the conductor and decreases exponentially with greater depths in the conductor. The electric current flows mainly at the "skin" of the conductor, between the outer surface and a level called the skin depth. Skin depth depends on the frequency of the alternating current; as frequency increases, current flow moves to the surface, resulting in less skin depth. Skin effect reduces the effective cross-section of the conductor and thus increases its effective resistance. Skin effect is caused by opposing eddy currents induced by the changing magnetic field resulting from the alternating current. At 60 Hz in copper, the skin depth is about 8.5 mm. At high frequencies the skin depth becomes much smaller.
Increased AC resistance caused by the skin effect can be mitigated by using specially woven litz wire. Because the interior of a large conductor carries so little of the current, tubular conductors such as pipe can be used to save weight and cost. The skin effect has practical consequences in the analysis and design of radio-frequency and microwave circuits, transmission lines (or waveguides), and antennas. It is also important at mains frequencies (50–60 Hz) in AC electrical power transmission and distribution systems. It is one of the reasons for preferring high-voltage direct current for long distance power transmission.
The effect was first described in a paper by Horace Lamb in 1883 for the case of spherical conductors, and was generalised to conductors of any shape by Oliver Heaviside in 1885.

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  1. Q

    I What causes skin effect in AC currents?

    My assumption has been it is the electromagnetic field starting from the center of the wire that pushes the electrons outward. However, this would also be true of a DC current, but it isn't. So why does an AC current cause electrons to move toward the skin of a wire? I don't recall ever seeing...
  2. Sibilo

    I Does the Skin Effect cause charge to accumulate on the surface of a conductor?

    good morning gentlemen, I would like to ask you a fairly simple question but which I am unable to resolve. Then considering the "skin effect", which involves an increase in resistance to the passage of current with consequent generation of eddy currents, this leads to an accumulation of charges...
  3. Narayanan KR

    A Question on Skin Effect and Eddy Currents

    When you try to create time varying magnetic fields in solid metals, there is severe heating due to eddy currents, when you increase the frequency, just like in NDT(non destructive testing) the magnetic field is pushed away from the core to the periphery due to eddy currents opposing the field...
  4. G

    Skin effect and electric shock question

    recently i saw a thread where skin depth was mentioned (I guess in one of my own threads) and then it got me thinking, well imagine we have a rather thick wire thick enough so that for a given frequency there is almost no current running in the middle of the wire due to skin effect. let's take...
  5. Jackson Lee

    An interesting question about the skin effect

    Hey, guys. There is something interesting about the skin effect, which also made me curious:wink:. Could you please help to solve it? The following is what I got from Wiki. It is said that, according to theory of induction, induced current would oppose the change of magnetic field. Then when...
  6. E

    Induction Heating Process Characterization

    Hi All, I'm working on a process involving induction heating. I'm heating up an irregular shape ss die to make a bond. My dilemma is in my understanding of where the eddy currents will be that generate the heat (based on skin effect). The clam shell die is pictured below. The right hand...
  7. E

    Maximizing Wattage in DIY Heaters: Impedance Matching with ZVS Power Supply

    Hi folks, I want to build a heater similar to this http://www.thermon.com/us/products.aspx?prodid=10 , using a ZVS power supply from ebay (such as this one -http://www.ebay.com/itm/381569526996?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT) ) As well I would like to replace...
  8. T

    Skin effect and magnetic field of a flattened conductor?

    A conductor with a large high frequency AC current causes a "Skin Effect" meaning that most of the current flows at the surface of the conductor. What does the skin effect look like if you have a conductor with one side flattened? And what does the resulting magnetic field look like? See...
  9. Anton Alice

    I What is the connection between the skin effect and electromagnetic waves?

    First of all, hello. I have a problem in understanding the skin effect. Often I read, that the skin effect is directly caused by eddy fields inside the conductor, which oppose the "desired" current flow. Problem at this is, that the eddy fields are not in phase with the desired current. The...
  10. Cedric Eveleigh

    Calculating current distribution in a HF coaxial cable?

    Hello, I would like to calculate the current distribution in a coaxial cable where the skin effect is significant. I asked this question on stackexchange and I provided pictures and more details there...
  11. dreens

    Frequency Components of a Lightning Strike

    Hi there, I recently attended a physics demonstration (Lightning show at Boston Museum of Science, my favorite exhibit obviously), where the educator argued that the reason she could safely sit in a Faraday Cage while lightning was striking said cage was the skin effect. As I understand it...
  12. G

    Understanding Skin Depth in DC and AC Fields: Confusion and Clarification

    Hello. The skin depth is nothing but measure of penetration depth of EM Wave when it is incident on the conductor. It is well known that the skin depth is decreased when the EM wave frequency increases. But thinking about DC field. We know that when DC is applied to metal (metal is installed...
  13. Dorian Black

    Electric/Magnetic vicious cycle

    Apologies for the melodramatic title. In studying AC current distribution in cables (skin effect), one can view the AC current as producing a time varying magnetic field in phase with the current itself (Ampere's Law). This in turn creates an electromotive force 90 out of phase with the current...
  14. H

    Skin Effect VS Gamma Ray

    Skin Effect: . where = resistivity of the conductor = angular frequency of current = 2π × frequency = relative magnetic permeability of the conductor = the permeability of free space ------------------------------ From Wiki According to Skin Effect, the higher the frequency, the less...
  15. A

    What is the working principle of wire grid polarizers?

    Hello forum, I have a few doubts on EM. 1. The skin depth formula for constant current(DC) shows that there can be current uniformly distributed through the cross-section of a conductor.However as there can be no electric field within a conductor(as per Maxwell's equations) there can be no...
  16. P

    Understanding the Skin Effect: Flux Linkage in a Wire

    I'm struggling to understand a key detail about this. My book divides the cross section of a wire into elementary filaments. It then states that the flux linked by the filament in the centre of the wire will be greatest, then this will decrease until at the outermost filaments the only flux...
  17. N

    I understanding how skin effect works

    I recently started working in low voltage electrical repair/upgrades in automobiles. I have a couple interns that i am working with and i truly want to be dam* sure I am explaining things properly to them. Me and my boss have had heated discussions on the subject and i believe him to be...
  18. R

    MATLAB Skin effect derivation and plotting in Matlab

    This is driving me crazy. The derivation of the current distribution in a long cylindrical wire is extremely straightforward, giving J(r) = J(a) \frac{J_0(k r)}{J_0(k a)} where J is the current density, a is the radius of the wire, and k is the complex wave vector, which in a metal (with...
  19. V

    Magnetic field and skin effect

    In Biot savart's law we have term for current flowing through conductor. Is there any equation which describes the effects of skin effect, radius of conductor and resistance of conductor on this current with which it is possible to know the current flowing through conductor without practically...
  20. Y

    Skin effect of transmission line

    I have to thinking about how the skin effect come into play in transmission lines with two conductors and dielectric in the middle. For normal skin effect, we consider a potential across a conductor as shown: Where the tangential E right above and right below the surface at z=0, are...
  21. E

    Skin effect, frequency and heating

    Hi. I'm trying to understand why smaller skin depths are better for induction heating. Skin effect means that the highest the frequency is, the thinest the skin depth is (or the depth is simply smaller because of the material). That means the section of the workpiece with electric current in...
  22. B

    Skin Effect in Electromagnetism: Detailed Explanation

    Can someone please explain in a detailed manner about skin effect in electromagnetism, particularly wanted to know why does this effect take place??
  23. C

    Understanding Skin Effect: Causes and Solutions

    Hey I know the conclusion of skin effect since secondary year of school, but I still didnt get it. I know the reason is because of eddy current. I couldn't include the link here as I haven't posted 10 yet. For the link, just search "Skin Effect" at Wikipedia. First paragraph of the cause in...
  24. L

    Skin Effect and shape of conductor

    Let's say we have 2 different conductors - one a round wire, another a round wire but with hollow core. The wire with the hollow core has higher resistance. But for the sake of argument, let's assume that it has the same resistance and the round wire. Will the skin effect be less for the...
  25. D

    Water Skin Effect in Plastic Pipe

    I need to Calculate the Skin Effect of water in a tube of X Diameter or Surface Area... The length of the Flow in the pipe would be 200 mm. I know that is short but it matters in this instance. The pressure of the water would be around 15 bar. I will post the flow rate through the pipe as soon...
  26. K

    Understanding Skin Effect: Causes & Effects

    Can anyone please describe the reason behind skin effect? All that I have come to know so far is that, due to higher magnetic flux density at the central region of the conductor compared to the region near it's surface, the effective inductance of the conductor is more at its centre and less...
  27. N

    Correct application of skin effect

    Hi all, I want to resonantly charge a capacitor, i.e. using a coil and diode combination instead of a resistor, in a very short period, which means a high current at high frequency. The problem is the coil. I read that at high frequency AC you get to deal with the skin effect, and also the...
  28. Y

    Induction Cooking, skin effect, hysteresis losses

    I've been looking into the induction heating a bit lately and have come up with a few questions. One is in regards to hysteresis losses. I know what hysteresis is and how it contributes to the heat generation, but how much of an effect does it actually have? Some articles I've read have...
  29. D

    What is scientific reason behind skin effect of conductors?

    What is scientific reason behind skin effect of conductors?
  30. R

    Magnetic field and Skin Effect

    I have been trying to understand the field theory from the basics and have come across a few things I have not understood a few things clearly: 1. The magnetic field strength is maximum at the center of the conductor and decreases with an increase in the distance from the center. I understand...
  31. Y

    Confused about plane wave and skin effect in conductor wire.

    I want to verify my understanding about skin effect and plane wave of conductor wire. In the diagram, assume long straight on z axis. Wire with radius = a and conductance = \sigma . Accouding to the equation shown, the plane wave is going towards the center of the wire only...
  32. C

    On Skin Effect and Microstrip Lines

    In the field of microwave engineering, skin effect is referred to when people talk about the fact that current, that is, electrons only flows on the surface of transmission lines, e.g. microstrip lines. I've checked many EM books--everywhere skin effect is demonstrated with both E and H...
  33. H

    Car Struck by Lightning: Faraday Cage or Skin Effect?

    Most places I've read say it's because the car forms a Faraday cage, but a few say that is incorrect and that it's actually from the skin effect. The notable case of the latter explanation is from the Boston Museum of Science: http://www.mos.org/sln/toe/cage.html This guy, Dr. Davis from the...
  34. A

    The Skin Effect in AC Circuits

    In DC circuits the charge carriers move uniformly through the entire cross sectional area of the wire. In AC circuits the current is constrained to travel in a thin "skin" just below the surface of the wire, effectively reducing the cross-sectional area of the wire. The effect becomes more...
  35. Phrak

    Calculating Total I2R Losses in a Conductor with Both AC and DC Currents

    References are available to calculate skin effect, RAC/RDC given wire gauge and frequency. But my problem is a complication of this simple calculation. Say I have a 1 Amp RMS AC current component and a selected wire size that gives me a skin effect of 7X the DC resistance. But I also have a...
  36. C

    Doubts on Skin effect & Electricity

    Hi all! This is my first post :D I came across skin effect which blocks propagation of an em-wave within a conductor... But doesn't the energy generated at an electric plant reach our house through conductors flowing for over a 1000 miles sometimes? If I have to consider it just as an...
  37. J

    Electric field from Skin Effect on a wire

    Hello All, I am wondering if when a sharp pulse is injected into a piece of wire, if that piece of wire produces a radially directed external electric whose magnitude is proportional to the skin depth of the current into the wire and the voltage potential of the input pulse. To elaborate...
  38. C

    What Causes the Skin Effect in High Frequency Currents?

    Can anybody explain the skin effect more clearly- why does the current tries to concentrate more closely to the surface of the conductor at high frequencies? what is happpening inside the conductor? thanks
  39. F

    Can potato skin effect the rate at which catalase breaks down hydrogen peroxide

    can potato skin affect the rate at which catalase in potato discs breaks down hydrogen peroxide? does potato skin contain the polysacharide cellulose?
  40. M

    Skin effect or total crossectional area

    Two cases: 1. A #12 solid copper wire is rated for 20a and a #12 stranded wire is rated for 25a the reason given for greater ampacity is increased surface area of the stranded wire called skin effect. 2. Does/is skin effect a consideration when current passes through a liquid or...