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Most of the resistance of the human body comes from the skin, as the interior of the body contains aqueous solutions that are good electrical conductors. For dry skin, the resistance between a person’s hands is measured at typically $500\: \mathrm{k \Omega}$. The skin varies in thickness, but on the average it is about $2.0\: \mathrm{mm}$ thick. We can model the body between the hands as a cylinder $1.6\: \mathrm{m}$ long and $14\: \mathrm{cm}$ in diameter with the skin wrapped around it.

(a) What is the resistivity of the skin?

So for this, I used the equation $R = (\rho*L)/A$. For Area, should I use the entire surface area of the body a.k.a cylinder?

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    $\begingroup$ Hi user2540416 - the question you were originally asking, for someone to check the steps you used, would be off topic here, but asking which area to use is a fine question. So rather than put this on hold, I edited out the parts which would be off topic. $\endgroup$
    – David Z
    Commented Mar 6, 2014 at 20:49

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In general, when formulae call for "area" they are talking about the surface area on which the force or whatever is occurring. Note that this is not always the entire surface area, it might just be the curved part of a cylinder for example. This is one such example, because we actually aren't interested in the end effects at the bases of the cylinder.

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  • $\begingroup$ I don't understand - what are they asking for then? I told them what area to use. $\endgroup$
    – Stella Biderman
    Commented Mar 6, 2014 at 21:15
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In the formula for the resistance A is the area perpendicular to the length. It can also be argued that it is the area perpendicular to the direction of the current going through the resistor.

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