Why is resistance across my arm-span so much less than across my face?

Question

This sounds like a strange question (it is) but, from a purely biological standpoint, why is the measured resistance across my hands (I measured 120k\$\Omega\$) so much less than across my face? I thought to ask this because the distance across my face is much less than my arm span.

More specifically, what makes the tissue in my face so much more resistant to charge (ion) flow than my entire arm-span?

P.S. I used a standard multimeter with resistance set at 2M\$\Omega\$ to get my readings - across my face doesn't even give a reading (too much resistance)

Answer 1

Hopefully this helps: Because resistance is proportional to material length and inversely proportional to cross sectional area (see below), I think it's safe to say that because your face has significantly lower cross-sectional area compared to your arm-span (probably by a couple orders of magnitude) that the length difference is negligible.

\$ R = \rho * \frac{L}{A_c} \$

Added to that (like what others have said before) a 'sweaty' surface like your hands likely gives excellent probe contact, while the less-moist (and hairier) surface of your face gives less complete contact.

All these factors result in much higher resistance across your face compared to your arm-span

Answer 2

Your skin surface resistance is what varies greatly. It will be affected by things like sweat, salt, and skin oils.

edit:

Skin oils can add a more resistive layer.

edit:

Try different distances in the same parts and like distances in different parts.

Answer 3

As Skaperen says it is all about the skin resistance. With an electrode in the meat under the skin, the resistance across the body will be much lower.

My theory is that you are able to obtain more contact pressure holding the meter probes in your hands, than when pressing them to your face.

Rather have someone else poke you with the probe, in the same way, in different places.

You could also put one probe in your mouth, which would be a low resistance connection to your body, and you'd have your hands free to probe all around.

Doing this, I think you'll find it's only the skin type and pressure that matter, not the distance across the body.

Answer 4

Is it possible that since there is likely more skin oils on your face, and more sweat on your hands that the results were affected?