basic experiment to show conductivity of people

andieje used Ask the Experts™

I am reading about a very basic experiment to show the conductivity of people:

1. Take plates of copper and zinc
2. Connect plates to a voltmeter (should read about 0.5 to 1.0V)
3. Get person to put one hand on each plate to complete the circuit

The electrochemical potential between copper and zinc causes the voltage. But apparently the voltage will change when people touch the plates and people with the sweatiest palms will have the highest voltage.

Please could you explain how people are affecting the voltage?

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I believe it's due to the water content of the body, the more hydrated the person is the easier the current will pass through. Hense people with sweaty palms will pass more current.

The body is a conductor, but a poor one basically.
>people with the sweatiest palms

It is this part that will cause the most difference. Dry skin won't conduct very well at all, but if the skin is damp and sweaty (sweat contains some impurities that allow the current to pass, pure water is an insulator) then electrical current can flow through the person via the metal-to-skin contact with the hands - the wetter the hands, the higher the current flow.

The person here is acting as the electrolyte between the plates of the battery so if the person-to-metal has less resistance then the 'battery' has less internal resistance and so will provide a higher current flow, therefore a greater voltage can be measured at the terminals.



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