It’s been an unusually dry winter here in southern California, which means static electricity is positively out of control. If I pet my cat in a single stroke from the neck to his tail, I get zapped at least twice.
Anyway, to avoid the more painful ZAP that tends to happen after getting out of my car, I thought it would be “safe” to ground myself on the supposedly nonconductive glass driver’s window, rather than touch the door frame first. I still get shocked, even though it isn’t as severe. This surprised me…does glass truly conduct electricity? Or am I missing something?
I used to think the world was against me. Now I know better: Some of the smaller countries are neutral.
Whoa. You’ve really got me scrapping the bottom of my memory bucket for this one. I think the glass in your window doesn’t conduct electricity, so touching it doesn’t ground you. Glass is an electrical insulator, just as your shoes probably are, so you build up an electric charge which is forced to be static. Only the metallic car is a conductor, which means that all that electricity turns into a small current all at once, resulting in a tremendous explosion which blows your arm off at the elbow and sets fires all over the county.
Okay, slight exaggeration. I might remember my electro-magnetics wrong, so beware. My personal way of avoiding the pain of the electrical shock, is to touch the car (on some non-polished surface, like the antenna) with a pair of keys. The static charge is still released, but since it is leaping off of the keys, instead of your finger, you don’t feel any pain.
Insulators probably won’t help.
This is a misconception I’ve run into before. (Most recently with my dad, who I’ve always regarded as one of the brightest people I know.) You have to touch something conductive to ground yourself. Touch something nonconductive has the same effect as touching nothing at all. Lightning rods are grounded with a heavy wire. that runs down to a metal rod driven into the ground. (BTW, grounding yourself during a thunderstorm is a bad idea.)
You can ground yourself with a 1 meg resistor before touching anything. I actualy did this in one appartment I lived in. The shocks I got in that house would knock you on your ass. The stereo would cut out out if you walked within 20 feet of it.
It’s very possible that you can get shocked by touching glass, but only with static electricity. It just wouldn’t be as strong as if you touched a piece of metal.
The reason you only notice it for static electricity is that a piece of glass has a high resistance. Electric current will not pass through it very easily. Static electricity doesn’t actually have to pass through an object, so the resitance doesn’t matter so much. Static works through simple coulombic attraction.
As long as there are imperfections in the glass, which there are bound to be, it can accept or give off a few electrons even if it doesn’t conduct electricity very well.
Safest bet to avoid a zap while exiting the car is to hang onto something metal on the car AS YOU ARE GETTING OUT of the car. This will bleed off any static charges as fast as they build up, saving you the discomfort of a blue hot spark perforating you someplace on your body.
FixedBack
“Moderate strength is shown in violence, supreme strength is shown in levity.”~~G.K.Chesterton 1908
Dammit, I misspoke…or at least, mistyped. What wasn’t clear in my OP was that I get shocked touching the glass–it was inaccurate to say I was attempting to “ground myself.” I’m aware that I have to touch something conductive in order to be grounded…what I should have said is I touch the glass window in attempt to avoid getting shocked, under the assumption glass is nonconductive. Nope. I still get shocked, while touching supposedly nonconductive glass.
Phobia: I had to do this also! I lived in a dorm suite one year that would shock the hell out of some of us (apparently the shoes some of us wore plus the carpet was a bad mix).
FixedBack: I do this also. In general, keeping in contact with earth (or a local) ground while you are moving (and would have been building up a charge) is an excellent way to avoid static electricity. The most bizarre situation I’ve experienced (and still do) is walking through the mall with my wife when she has her winter coat on. I’m not sure what’s rubbing against what (no pun intended ;), but almost every time I touch her I get shocked. I usually end up holding her hand or putting my arm over her shoulders (with my finger touching her neck) to avoid building up a charge between us. If my finger loses contact with her neck for a second or two, I get shocked almost every time I touch her again.
Static electricity is usually associated with NON-conductors. You can build up static electricity by rubbing your hair with a balloon, neither of which are what you might call good conductors. Rubbing a glass rod with a silk handkerchief also works pretty well.
Oh, I understand now Ruffian. I wonder if there are enough impurities on the glass to form a conductive surface. You know, like a thin layer of grit and road goop that somehow forms a chain of available electrons, all the way to the metal around the windshield.
While the glass itself isn’t terribly conductive, there may be a build-up on it that is. In particular, it probably has a hydrated surface layer. This layer may be more conductive than the glass itself. In fact, when I was testing glass samples for conductivity and other electrical properties back in my grad school days, I had to make sure the electricity was going through the sample, not just around the outer layer of it.
The reason is that electric charge builds up and has no place to go… it usually likes to head for ground. It is more likely to build up on insulated metal, but the charge can accumulate on practically any surface that doesn’t have a path to ground. The real problem is that your car is completely insulated from ground by the tires - it doesn’t matter where you touch it on the shell, you’re likely to get zapped.