Static Shocks
August 14, 2014 8:34 PM   Subscribe

I was wondering if the static shocks that a person normally gets in the winter are caused by an excess of electrons, a deficiency of electrons, or if it happens both ways but just depends on the circumstance.
posted by 517 to Science & Nature (8 answers total) 2 users marked this as a favorite
It's due to drier air; with fewer water molecules in the air your body hold a charge better. The excess electrons are less likely to skeet off of you into the air around you.
posted by sebastienbailard at 8:37 PM on August 14, 2014

But do you have a net positive charge or a net negative charge just before you're zapped?
posted by Chocolate Pickle at 9:11 PM on August 14, 2014

It's going to depend. Specifically, it depends on where the materials that are being charged are on the Tribolectric series. If it's something that tends to be more positively charged, it will suck electrons back when it discharges; if it's something on the negative side of the series , it will push electrons off.
posted by Betelgeuse at 9:25 PM on August 14, 2014 [1 favorite]

I have a thing at work that can both build up a little static charge in the winter and show me which way the charge is going relative to a grounded standard; it seems to run about 75/25 -/+.
posted by tchemgrrl at 9:25 PM on August 14, 2014

Yep, it's the humidity (or lack thereof).
posted by Invisible Green Time-Lapse Peloton at 10:14 PM on August 14, 2014

as an aside, the number of extra electrons you're picking up/losing is ridiculously small (the electromagnetic force is really strong...think of hanging off the bottom of a metal bridge by one of those big boat magnets...that's the magnetic force in something about the size of a grapefruit holding you up against the gravitational force contained in the entire earth) or, as a physics professor once told me 'if you and I had just 1% more electrons in our bodies and tried to shake hands, the amount of force pushing us apart would be enough to shove the earth out of its orbit.'
posted by sexyrobot at 11:05 PM on August 14, 2014

As a weak conductor with a fairly large surface area, an electrically isolated human body is probably capable of maintaining a considerable charge of either polarity (i.e, it has considerable capacitance).

However, according to Betelgeuse's link, skin is quite high up toward the + end of the triboelectric series, meaning that almost anything you rub up against will give you a relatively positive charge.

The solid Earth itself has a large net negative charge, and any conductor in electrical contact with it will share that charge

Therefore, the shocks a person gets in the winter are probably due to a deficiency of electrons in most cases.
posted by jamjam at 11:09 PM on August 14, 2014 [1 favorite]

On the other hand, the classic static shock scenario is when you scuff your shoes on the carpet, so it's not skin but synthetic rubber (-) or leather (+) that's doing the rubbing. Judging from the list, your net charge depends on whether you're dressed up or down!
posted by moonmilk at 4:51 AM on August 15, 2014 [1 favorite]

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