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I know that water with salts is a good conductor-However wetting a hand only adds water to a not very conductive surface. How does water actually reduce the resistance of skin? The way I am seeing it is that as opposed to just a wire touching skin, the wire is touching water then touching skin, which still does not seem to imply we would have less resistance.

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How are you testing this? Are the two wires touching the same patch of wet skin? If so the current will take the path of least resistance which is the water on the surface of the skin. –  Will Jun 9 '13 at 23:57
    
Even if it's just two wet patches that are isolated, can't it kill you? –  Anthony Jun 10 '13 at 5:35
    
I'm not sure how that is an answer to my question. –  Will Jun 11 '13 at 4:25

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First of all, don't try this at home.

You may consider your body as a resistive element (with total resistance about 1000 Ohms). This depends on personal parameters, given voltage and many other factors, but let's say it's around that. It is your total (equivalent) resistance, but each part of body has it's own, but combining them together will lead to this ca. 1 kOhm.

If you touch a wire, the current flows through the body. There is a voltage drop on it, so you calculate current dividing voltage by your body, if you are still able to ;-).

When you are wet, water makes a surface on your skin. This is equivalent to connect your body with this water surface in parallel. The total resistance of your body and water connected in parallel is smaller, but current through the body itself does not change, but it is larger in total as some flows through water. Some electricians still believe that keeping hand in pocket while touching a wire with the other hand, in case of failure, will make current flow through the hand in pocket and bypassing the heart. This is very hard to prove, however.

For example, let's consider you have wet arm from fingers to a shoulder. If it is wet, you add water in parallel and thus lower resistance of arm. So shoulder has higher potential than it would had in case of dry arm. This means that larger current flows through your heart.

But --

Current can in some part lower body resistance: because water tends to flow under your skin, which is not a solid barrier. This might be because of energy of the flowing current, increasing the temperature, and making some dielectric phenomena on the cellular level, that destroy skin surface.

All these things apply to some high voltage, say 200 V and more. If you touch 24 V with a wet hand, you probably will not see the difference.

To read more about human body resistivity, you might like to read this article. Please notice (Table 1) that fat has much larger resistivity than other organs. Your skin has always fat on it and it is used by criminal police to find fingerprints. If it is wet, the fat surface could be thinner.

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This answer sounds reasonable (i.e. that the area of connexion with the wire is raised). However (speculation on my part here), I wouldn't be surprised if part of the effect is that water dissolves ions and electrolytes in the skin, thus reinforcing what Voitcus is saying. –  WetSavannaAnimal aka Rod Vance Jun 28 '13 at 11:13
    
Well, yes, some osmotic changes within salt of skin can occur, but I don't know the impact of this. –  Voitcus Jun 28 '13 at 12:35

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