'Skin Effect': It doesn't apply in Violet Wands

by Uncle Abdul

There is a belief among some electric play users of Violet Wands that they are safe, i.e., no currents go through the heart, because of "Skin Effect." By this phenomenon, it is reasoned, the currents from the Violet Wand arcing to the skin will travel only on the surface of the body's skin and not in the body interior. Thus, it is argued, no currents can go through the heart. In this way it is felt that Violet Wands are therefore intrinsically safe and can therefore be used for electric play above the waist.

Because of the reliance of players in their belief of this line of reasoning thinking they're totally safe in that no currents will ever go through the heart it is best that the phenomenon known as "Skin Effect" should be further explained.

JUST WHAT IS 'SKIN EFFECT'

Skin Effect is indeed an electrical phenomenon. In fact electric power companies use it as an important factor in designing power transmission lines. Because of Skin Effect they can use hollow electric power transmission conductors because the currents will tend to stay on the outside of such conductors.

"Ah-ha," you say, "So the same must be true in or 'on' the body." Well, not quite. The "Skin Effect" that electric companies depend on is really a magnetic effect. Let's take a look at what that means.

You've probably heard or know that a moving current in a conductor will produce magnetism. If you don't know this, take a moment to perform the following experiment. Open the hood of your car. Find the battery, and look for the main battery cable that goes to the all the circuits in the car. Now turn on the car's headlights. Then going back to that battery cable place a small, cheap, magnetic compass next to the cable. What do you notice? You'll most likely will notice that the needle of the compass will align itself parallel to the cable. Magic? No, just magnetism caused by the current running through the battery cable. Not convinced? Turn off the headlights (and all other electrical devices in the car) and do the compass test again. The compass needle will point in a different direction (unless the battery cable lies parallel to the magnetic north-south line of the earth). This is exactly the same thing Hans Oerstad the Danish physicist and chemist (1771-1851) discovered nearly 200 years ago.

Michael Faraday (1791-1867), English scientist, discovered shortly after that if you move a wire through a magnetic field, a current will be produced running through the wire. Coils of wire spinning in a magnetic field are what make your car's generator generate electricity. It's also why the telephone magneto play toy works.

Along comes a third scientist, Lenz, who combined the discoveries of the other two and came up with his own law. In it he said that as a current moves through a conductor it produces a magnetic field (Oerstad's Law, right? Right.). If that field changes because the current changes—like in alternating current (or AC) that comes from the power company to your house—its the same as if the conductor were moving in a magnetic field (enter Faraday, stage left). This should produce another current, right? Right.

Now it works out that this second current that is produced runs in the opposite direction of the first. But the first current is the one that produces the second one right? Ri-i-ight. (Actually it's a changing first current—AC—that will produce the second which will always run in the opposite direction. We say this second current opposes the first one.

What this looks like to somebody studying the currents in the conductor is that somehow the resistance (opposition to current flow) somehow got larger. But this only works with AC currents. The DC (Direct Current) resistance of the conductor is still the same for both DC and AC currents. What we're really seeing is the phenomenon of 'Self Inductance,' which is something you only see with AC currents running through a conductor.

So why is this important? Well for one Lenz's Law is what makes electric meters for your house work. It's also the reason why transformer cores are made with laminated sheets instead of a solid metal piece. And finally power transmission line engineers go orgasmic at it because now they can use hollow conductors on their power lines thereby saving weight, cost of material, etc. Yeah Lenz!

Lets take a closer look at this last point.

If you look at a cross section of a conductor carrying an AC current, each current element—electrons in this case—as it moves generates a magnetic field. Now magnetic fields of the same polarity (north or south) will tend to repel each other. (Try this by seeing how hard it is to force the north poles of two magnets together.) Because of this the electrons will tend to move themselves apart. Now when you combine this with what we know about Lenz's Law, we can see that the currents will stay towards the outside of the conductor. Atta boy Lenz!

Now remember, this only works for AC currents, and to be meaningful we have to talk about conductors that are about 1-1/4-inches or more in diameter at power line frequencies of 50 - 60Hz. Ordinary house wiring of about 1/8-inch in diameter are hardly affected.

WE SPEAK NOW OF KINGS AND VIOLET WANDS AND OTHER THINGS

So let's go to the 'heart' of the matter. Is "Skin Effect" a factor in Violet Wands? Does the current arcing onto someone's skin stay only on the surface of the skin?

Well, let's see. The Violet Wand uses AC electricity, right? Right. The body is a conductor, right? Well, kind of. Current will pass through a body like a conductor, but there's such a high resistance (50,000 to 1,000,000 ohms for dry, unbroken skin) that it's more like an insulator—unless you're hit with high voltage like lightning or with an electric chair which is what you might get to sit in if you don't understand electrical play.

Now "Skin Effect" used for power transmission lines depends on really high AC currents (10's of amps) to produce enough magnetic effect in order for the "Skin Effect" to do it's thing. The currents in a Violet Wand are really low. Yes, they do produce a magnetic field that does constantly change, but these magnetic fields are so weak they're going to have little if any "Skin Effect" effects.

HAH! I GOT YOU UNC' BECAUSE THE VIOLET WAND IS A HIGH VOLTAGE DEVICE, IT'LL WORK LIKE ELECTROSTATIC CHARGES THAT STAY ON THE SURFACE OF A BODY. I REMEMBER THAT FROM HIGH SCHOOL PHYSICS.

Kudos on you memory, but do you want to stake your life on that? Actually you can't have it both ways. You either have to say that there are actually currents coming from a Violet Wand or that it only produces electrostatic charges (excess or deficiency of electrons). Now I've already shown in "Juice-Electricity for Pleasure or Pain" that a Violet Wand does produce small AC currents that do run through the arc and through the body (see Chapter 8). Actually this surface charge idea is probably what people have in mind when they speak of "Skin Effect," but you're probably convinced by now that's not so. And because we know the Violet Wand produces AC currents, thus the surface electrostatic charge idea goes the way of the great auk. Next.

AHH! BUT THE VIOLET WAND IS A HIGH FREQUENCY DEVICE—ALMOST RF. IN HIGH FREQUENCIES DON'T THEY USE HOLLOW CONDUCTORS FOR THAT? WOULD IT WORK THE SAME IN A BODY?

In really high frequencies like microwaves (500-5000 mega Hz) used in Radar and microwave ovens, yes they do use what are called wave guides which are very much like hollow conductors. In fact many of them are just plastic tubes coated with a thin gold plating. And you don't even need to go that far. For some of you that still use rabbit ear TV antennas, the cable that connects that to your TV is what is called 'twin lead.' The two conductors are held apart some specific distance because that's the only way the TV signal currents (at 80-110 mega Hz) can flow. Radio amatures still may use a larger type of the same thing for some radio transmitters (at 1-400 mega HZ). If you tried to substitute say a lamp cord for twin lead on a TV, the signal would never get through.

Why does this work? Oh boy! That really gets complicated very fast and is difficult to come up with a layman's explanation. The math really gets hairy too. It has to deal with a fourth scientist, a Scot, James Maxwell (1831-1879), who discovered a whole series of electrical laws in 1873 called oddly enough Maxwell's Equations. Actually he lumped Oerstad's and Faraday's and several other laws together into a nice, elegant set of mathematical equations that relate electrostatic and magnetic fields—or oddly enough called electromagnetism—together. If you want to delve into them there are many excellent references to look into. The American Radio Relay League (ARRL) does a nice job on this. Be prepared to wade through some math though.

In short, using Maxwell's Equations you can show that for very high frequencies like radio and microwaves, the electrostatic portion (and hence current) of an electromagnetic wave tends to 'stay' on the outer portion of the wave. Thus the currents will stay on the surface of the wave guide or on the outer conductors of a twin lead. (In fact designing 'wiring' for microwaves is more a machinist's and a plumber's job than it is an electrical technician's job.)

So, does a Violet Wand qualify? Can a human body work like a wave guide and have the currents stay only on the surface of the skin and not run through the heart?

Well, the Violet Wand does use a Tesla coil and a vibrator to generate the high voltages, and there are some high frequencies present. The only trouble is that the 'fundamental' or base frequency of the unit is still 60 Hz—household power line frequency. By the time you get out to the 1 mega Hz component of the Violet Wand, it is probably so much "in the mud" (as we say) that the wave guide effect damn near vanishes.

Now the human body is more like a wave guide turned inside out. You have an insulator—skin—on the outside and the conductor—oopy goopy stuff—on the inside. Sorry, that makes an anti-wave guide rather than a wave guide. Besides, a wave guide needs constant geometry to work. Remember the twin lead TV wire? Human bodies are ...well... wonderfully curvy—great for play, but lousy for waveguides.

DON'T THROW IN THE TOWEL. VIOLET WANDS CAN STILL BE USED FOR PLAY.

In the book Juice I spend a lot of time talking about a Violet Wand. You just need to realize that it does depend on running a current through the body in order to work. What you have, however, are several factors working to save you arse—or more specifically your heart.

For one you have a whole series of high resistance working in your favor. There's the resistance of the gas inside the tube. There's the resistance offered by the glass of the tube. There's the resistance present in the spark. And finally there's the resistance of the skin—yeah skin! So even though you're working with high voltages, all of those high resistance really work to keep the currents going through you very, very low.

So here you have the situation once again of currents going through the heart—just like in TENS Unit. The question is, "How much, and is it dangerous?" And that gentle reader is what you must understand when you play with any electrical play toy. You need all the information—in Physics in Physiology and in Psychology—to assess the risk and to make informed, intelligent choices around those risks. It's really up to you and your partner. To do otherwise or to depend on "old electrical wives' tales" is quite literally "whistling in a graveyard."

Play SAFE through UNDERSTANDING.

Uncle Abdul
Khabarovsk, Russia - 1998

Tags: History | Skin