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Does a dry human body in contact between 230 volt mains voltage and ground has any form of capacitance ? Shouldn't there be some, or else is it just resistance ? I was thinking whether the Xc component plays any part when a person gets electrocuted

user132257
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  • Google human body model. See https://electronics.stackexchange.com/questions/312222/a-question-about-the-current-value-in-a-mains-tester – winny Jun 23 '17 at 05:35
  • Unless mummified, there's no such thing as a *"dry human body"* ;-) – Roger Rowland Jun 23 '17 at 07:07
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    You can scroll down to my answer here, https://electronics.stackexchange.com/questions/152090/measuring-feline-capacitance And see that the human body has ~200 pF of capacitance. At AC frequency this is irrelevant when compared to your resistance. – George Herold Jun 23 '17 at 12:23

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Capacitive reactance (Xc) is a measure of a capacitor's opposition to AC (alternating current). Just Like the Resistance. When you come to contact with AC, the opposition to current for a human body must be the total impedance, considering your body capacitance and resistance. Given by the Following Formulas.

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According to this Link http://van.physics.illinois.edu/qa/listing.php?id=6793 The external human body resistance is about 1k to 100k Ohms, and the internal resistance is 300 to 1000 ohms. Only a thin layer of dry skin separates the internal resistance from an external object.

The human body capacitance to a far ground is 100-200pF, which is really a minimum value. Noting that the Capacitive reactance depend on the frequency.

So your overall body impedance will be quite significant because of the very small capacitance that produce a big Xc in the range of Mega Ohm. Helping to limit how much current can traverse your body.

But note that you only need to pass a current of (6 to 200 mA for 3 seconds) to make it fatal, and that's can happen when your body becomes sweaty decreasing your overall impedance.

So yes your Xc does play a role during electrocution, since its part of your body impedance which is the opposition to current.

All note that these parameters are not constant they vary from body to body.

Chad
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  • Interesting how Electroboom was able to get a capacitance 25-50 times greater than that expected 100-200 pF at power line frequencies https://www.youtube.com/watch?v=vNpGoNP1tGQ – ManRow Aug 11 '21 at 11:11