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Getting zapped getting out of the car. Details....


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We've all been zapped getting out of the car and touching the door. It's static electricity build up that gets discharged at the fingertips. The situation is worse with synthetic clothing, rubber soles, and dry air. I understand what's going on at a high level, but am curious about the details. My understanding is that both my body and the car are charged (differently) due to my clothes rubbing against the car seat etc.. The car may also be charged due to road friction etc., but I don't know which one is a bigger contributing factor to the static build up (clothes rubbing, or car's road/air friction). Anyway, I cannot verify what I think is going on with my (silly) experiments. In all cases, let's assume I have rubber soles (good electrical insulator):

 

(1) Car stops, I step out, then touch the metal door -> get zapped. Explanation: When I step out I still am charged (soles insulate). There is a potential difference between me and the car, and that's what is being discharged when I touch the car. 

 

(2) Car stops, I step out, then touch some other grounded metal like a metal pole -> get zapped. Explanation: When I step out I still am charged (soles insulate). There is a potential difference between me and the pole, and that's what is being discharged when I touch the pole. 

 

(3) Right after (2), I must be back to neutral. Immediately after that, if I touch the car -> get zapped. Explanation: Even though I am neutral, the car is still charged, and when I touch the car, I feel the discharge.

 

(4) After the car stops, and I am still seated, if I touch the metal door, nothing happens. I lift my hand off the metal and then follow (1) -> get zapped. If there was a difference between me and the car, why doesn't that discharge when I touch the metal frame (while still seated)? The second half of this test (i.e. doing (1)), confirms that the car and I did not balance out. This is confusing to me.

 

(5) After the car stops, I hold on to the metal door, step out while holding the door, lift my hand off the door, and then touch it back again, nothing happens. So somewhere during this process the car and I must have come to the same potential.  When is this happening as I never feel the zap?  Also, by the end of this process, are we both grounded? I thought the soles would have prevented me from grounding. At the end, this process is what is recommended for avoiding the zap, and I can confirm it works, but I cannot explain why.

 

(6) After the car stops, while I am still seated, I touch the ground (road) with my fingertip. No zap. Why didn't I discharge through the ground (bare fingertips)? Then I follow (1) and get zapped. This means I was still charged after touching the ground. I read somewhere that the ground still has a high resistance or something, preventing a discharge from my finger. Is that so? If I had touched an external metal (say a pole), I would have discharged, is this correct?

 

So can someone explain what exactly is going on? I am confused. Especially why (5) works but (4) doesn't. If one of the reasons that (5) works is my feet touching the ground and discharging through a larger area that I am not feeling, this does not explain (6) or (2). 

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I read about this years ago. 

Quote

Once you have built up a big enough static charge, an electric shock is almost inevitable. The moment you touch a conducting material such as metal, the excess electrons jump between your hand and the conductor, giving you a shock.

Let’s take a closer look at what happens while you are in a car. As you enjoy the ride, electrons are exchanged between your clothes and the car seat, building up collections of excess charges. By the time you get out of the car, you have accumulated an overall charge, whilst the vehicle carries the opposite charge. To make things worse, the rubber car tyres and the soles of your shoes are insulators, stopping the charges from escaping to the ground. As you reach to close the metal door, electrons leap between your finger and the car… zap!

 

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It's not the current that stings, it's the arc.  If you hold a brass key tightly in your hand and touch the key to metal, the spark will jump between the key and the metal.  You'll hear it snap, see the arcing, and feel nothing.  If you hold the key loosely, it might arc some between your fingers and the key, so be sure to hold it tightly.

 

Another trick is to open the car door and grasp some metal of the car body or door with your bare hand before sliding out of the seat.  You'll be grounded the whole time and won't build up a charge.

Edited by Neptune48
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Thank you all, but these don't clarify it for me. 

 

18 minutes ago, Neptune48 said:

Another trick is to open the car door and grasp some metal of the car body or door with your bare hand before sliding out of the seat.  You'll be grounded the whole time and won't build up a charge.

This is what I described in (5) of my first post. It works as I acknowledged, but I don't understand why it works while (4) does not work. When you say I will be grounded the whole time, is it the car being the ground? If that is the case, in (4), why don't I discharge whatever static I have to the car? 

 

I tried another experiment today. After I stopped, while still seated, I held onto the car's metal frame with one hand, and I put my other hand on the ground (asphalt/dirt). Both bare hands. No zap. I held that position for 10 seconds. I thought by then I would have discharged all my static, and so would have the car. Then I lifted both hands, stepped out of the car and touched the door. Bang! Got zapped again. 

 

So what I observe does not match what I think is going on, and clearly I have gaps in my thought process, so that is what I am trying to figure out. Ground vs good/bad conductor vs which objects are charged during all this stuff etc. I am confused. 

 

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39 minutes ago, Neptune48 said:

It's not the current that stings, it's the arc. 

 

It's not the current that stings, it's the voltage.

 

The 'shock' from this kind of static electricity can have very high voltage but is very very low in current.

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10 minutes ago, Janissary said:

Then I lifted both hands, stepped out of the car and touched the door. Bang! Got zapped again.

 

Did you slide your butt on the seat as you got out? That will build up a charge, just like sliding your feet on the carpet then touching a door knob.

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18 hours ago, Janissary said:

We've all been zapped getting out of the car and touching the door. It's static electricity build up that gets discharged at the fingertips. The situation is worse with synthetic clothing, rubber soles, and dry air. I understand what's going on at a high level, but am curious about the details. My understanding is that both my body and the car are charged (differently) due to my clothes rubbing against the car seat etc.. The car may also be charged due to road friction etc., but I don't know which one is a bigger contributing factor to the static build up (clothes rubbing, or car's road/air friction). Anyway, I cannot verify what I think is going on with my (silly) experiments. In all cases, let's assume I have rubber soles (good electrical insulator):

 

 

I don't have straight answers, but maybe a solution.

 

I experience similar problems, but with my computer. My chair charges me badly, and when I want to plug in something (USB cable, memory stick) I discharge myself accidentally on the computer. Usually it continues working for a few more seconds, then it slowly crashes. The modem also crashes, and it takes a few minutes to get everything working again. Plus there's the risk of permanent damage

 

Recently I made a simple grounding point near the USB connectors, by running a small electrical cable from the computer chassis to the exterior of the computer. But that only worked partially: with a strong discharge the computer still crashed. Plus it was annoying to still get zapped badly.

 

After a bit of thinking I decided to add a resistor to the grounding point. I used a 100K Ohm resistor. The discharging is now slowed down sufficently to avoid computer crashes, and I no longer get zapped. Seems to work! I'm now thinking how to convert my improvised solution into something permanent and nice.

 

Maybe you can make a grounding point with a resistor on your car door?

 

Rob

 

 

Edited by Rob de Bie
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Put a anti-static strap on your car. You can still buy then. This will send any charge to the ground and end all your problems.

 

You are confusing grounding and bonding. Obviously while in your car you are bonded to your car and you are at equal charge. You are getting a zap whenever you touch something that has a ground path. That is clear to me.

 

You are also getting zapped whenever you have grounded yourself and touch the charged car again.

 

The most amount of static build-up will be from the air/tire friction on your car. I know a fuel truck driving on a gravel road on a dry hot day can build up in excess of 80,000 volts.

 

Sounds like you shoes are not insulating. They are the return path to ground each time you are zapped. Most shoes are not designed to be electrically safe. You need specific shoes to ensure electrical safety. Conductivity is dependent on the material they are made of, how thick that material is, if there is dirt or moisture, etc.

 

Whenever you are bonded to your vehicle, you aren't getting zapped.

 

You don't say what type of climate you live in.

 

Your car is building up a lot of charge. Get an anti-static strap that attaches to the frame and draws the static-charge to the ground.

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31 minutes ago, Grey Ghost 531 said:

They make braided steel grounding straps for cars too, It bolts to the frame and drags very lightly on the ground.

 

The metal braided ones do exist although they don't last as long as the rubber ones. The rubber ones have a dielectric constant that does permit discharge of static charge.

 

 

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Thanks everybody for your input. It made me think more and do one more test. I think I got it now! At least, it explains all my observations and everything seems to make sense. Here is what I have concluded:

 

The most significant time of charging is when I am getting out of the car (thanks Moose135 for pointing this out). I believe there is very little or no static build up while you are driving. I think the carbon added tyres are helping with static discharge, so the car is more or less grounded at all times. Here is how I came to this conclusion (I will continue numbering from my first post):

 

(7) I drove around for a while, then wanted to see if the car and I had been significantly charged. I pulled up to a drive thru, stuck my hand out of the window and touched the metal frame of the drive thru. No zap. Drove more, touched the metal pole of a stop sign, again nothing. Drove home, touched the metal frame of the garage door, again nothing. So, if the car and I were charged (Scooby, I agree that the car and I are bonded so would be at the same potential), I should have felt the zap touching these external metals while still seated. I did not.

 

(8) After I pulled into the garage, I got out of the car in the usual way (did not touch the car door), went to touch the garage frame. Bang! I got zapped. It was at the intensity that I normally feel. So this very experiment tells me I must have been charged while getting out of the car, because I had already touched the very same metal frame just a few seconds prior to that.

 

(9) I was at a coffee shop. The car had been parked for more than 30mins. I came back to the car, touched it, nothing happened (as expected). Then, I sat in the car and without doing anything else, I got out and touched the door. I got zapped at the usual intensity I feel. So clearly, this charging must have happened as I was getting in/out. 

 

Now all these explain very well all my observations in my first post. For instance, (5) works to alleviate the zap because the car is acting as ground (like Neptune48 was saying). On the other hand, (4) does not work because the car and I are at the same potential anyway (like Scooby said), plus I believe there is actually no significant charge on us after all (see test (7)). 

 

So if anyone is interested, the takeaway is that in passenger cars, the most critical time for static charge build up is while getting out of the car, not while driving. I think this is the same reason why they strongly urge you not to get back in your car while pumping gas. Because as you get out, you are getting charged, ready to cause a spark.  I think the car tyres serve as appropriate conduits for grounding that prevents in-drive static build up. 

 

In terms of avoidance, many tricks have been offered, but the one I use is (5) of my first post. It works 100% of the time, every time. 

 

 

 

 

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I don't agree the most significant time for static build-up is when you are getting out of the car.

 

That is when you get zapped, you are the return path to ground for the built up charge stored on your car. You are providing the ground.

 

You didn't mention what sort of climate you are in, although I am betting it is a dry one.

 

We did testing on fuel trucks in the Canadian Forces. There is significant static charge built up when driving and fueling. That is why we bond and ground our vehicles.

 

I've seen guys get zapped by CF-5 canopies that weren't discharged after landing. It isn't pretty, first time I've saw a human fly.

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I have found getting out of the vehicle is the reason for static build up. The multiple layers of clothing rubbing and the seat of your vehicle tends to create this situation. My daughter used to get very car sick as well. So what I did to handle both situations was to get the vehicle grounding strap (my daughter stopped getting car sick after it was installed) and I would spray diluted laundry softer onto my seat. This took the ability for static charge build up...never had an issue with it again.

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10 hours ago, Scooby said:

I don't agree the most significant time for static build-up is when you are getting out of the car.

 

You didn't mention what sort of climate you are in, although I am betting it is a dry one.

 

Agree with scooby, the static buildup is due to lots of things, not just your butt sliding on the seat when you exit the vehicle. Rolling friction of tires, air friction while in motion, seat springs and cushions soaking up bumps, even lowered humidity due to driving with windows up and the AC on. 

 

Your "tests" are more subjective than conclusive. Do some reading on triboelectricity and electrostatic induction.  Without an understanding of the physics involved in static electricity and electrostatic discharge you can't know your "test" results are conclusive.  "It hurts when I do / don't do this" just tells you when, not why.

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In the interest of determining the truth, I will disagree and would be happy to change my mind with convincing explanations. I have been confused as hell (hence my first post).  But after gathering everything I have observed so far, the conclusion I have come to makes sense to me. Again, happy to be convinced otherwise.

 

I am restricting my conclusion only to passenger cars, city driving, and recent tyre technologies. I think this applies to many people here and I have been trying to understand all the events that lead to the zap. All along, I knew how to avoid it, that was not the problem. With that, my conclusion is: "The static build up that eventually manifests itself as the annoying zap is not due to the friction induced during driving, but rather due to the charge build up while getting out of the car."

 

Also, I'm excluding all instances of fuel trucks, aircrafts, fuel tankers, and cars with very old tyre technologies. There are other phenomena there that cause significant static build up (turbulence in fuel causing friction, high speeds, bulk fuel motion etc.). I am aware of the precautions used in these cases such as chains or grounding strips on fuel trucks, grounding activities in aircrafts, static wicks to mitigate in-flight static build up etc. So yes there are these cases where motion induces significant static build up and it has to be dealt with carefully.

 

However, I believe I was making the mistake of transferring all this to my everyday driving. I thought until recently that the reason I was getting zapped was the static build up that was caused by my driving. I no longer believe this to be the case based on my recent observations. I don't want to generalize this beyond my own experiences, but if I had to bet, I would say for most passenger vehicles nowadays, my conclusion holds true (again, no extreme speeds and only new tyre tech). 

 

This is not to say that all the motion/friction of the car does not create static. I believe it does. But they key here is that car tires are now such that they are more conductive than they used to be. Hence, they ground the car for the most part, so significant static build up does not happen in these cars while driving. While rubber is a good insulator, my understanding is that carbon is added to modern tires to make them more conductive.  Now I cannot claim that I know this for a fact, but my explanation (i.e., no significant static build up while driving), has so far explained "everything" I have observed. That is why I am willing to accept it as the null hypothesis

 

I want to point out in particular my test (7), which is in a few posts above. If there was significant static build up, why did't I feel the zap when touching those three external metal surfaces all of which were grounded? Then, follow that with (8) and (9). So there is a double whammy situation here: I not only observed that there is no static build up while driving (see 7), I also observed there is considerable build up as I was getting out of the car! By considerable I mean a build up that intensity-wise results in a zap I consider annoying. 

 

You may claim that my 'tests' are subjective and not conclusive. Yes they are subjective because I did those tests. And yes they are not conclusive because I can only form a null hypothesis. I don't know what else I can say here.... Also, I disagree with the remark that, quote: "It hurts when I do / don't do this" just tells you when, not why." The timing of when it hurts vs does not hurt gives me insight into the presence or absence of a static build up. 

 

I anticipate by now I may have bored many people. But the tests I ran are not difficult to repeat independently. I would be more than delighted to hear your observations, trusting that everybody would report their honest experiences. 

 

1 hour ago, habu2 said:

Do some reading on triboelectricity and electrostatic induction.

 

 I did. I haven't found anything that refutes my conclusion. As a matter of fact, these are concepts I already know. But that knowledge did not prevent me from the confusion I described above. 

 

 

 

Edited by Janissary
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You are assuming you touched grounds in test (7).

 

Your car is building a charge when driving. The only time you are getting zapped is when you are actually closing the circuit and sending the charge to ground. It is as simple as that.

 

Buy an anti-static strap and your problem will be gone, I am 100% certain of this.

 

I have a strong background in electronics as both an avionics engineer and biomedical engineer. I have designed prototype medical research devices in a university research laboratory. I built these nanotechnology devices from the component level up. All of the components  were surface mounted and designed by CAD. Being a prototype device nothing was built through automation. What I'm trying to say is I know a thing or two about static-electricity and the causes an hazards associated with it.

 

Your car is a giant capacitor when you are driving it.

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38 minutes ago, Scooby said:

You are assuming you touched grounds in test (7).

I have strong reasons to believe those metal surfaces were grounded. The stop sign pole was buried in dirt. Also, see (8). It was not my shoes closing the circuit, it was the garage door's metal frame, as I apparently carried all the charge with me walking back to the garage door.

 

38 minutes ago, Scooby said:

 

Your car is building a charge when driving. The only time you are getting zapped is when you are actually closing the circuit and sending the charge to ground. It is as simple as that.

I disagree with the first sentence, but agree with the second. My claim is that what is being discharged (the zap) is the static I build up as I am exiting my car. It is not the static that build up when I am driving.

 

38 minutes ago, Scooby said:

 

Buy an anti-static strap and your problem will be gone, I am 100% certain of this.

 

I have a strong background in electronics as both an avionics engineer and biomedical engineer. I have designed prototype medical research devices in a university research laboratory. I built these nanotechnology devices from the component level up. All of the components  were surface mounted and designed by CAD. Being a prototype device nothing was built through automation. What I'm trying to say is I know a thing or two about static-electricity and the causes an hazards associated with it.

I respect your background and believe you know quite a bit. It is clear from your posts. However, just like me, you are making the mistake of taking your knowledge in electricity/electronics, circuity and all the things you have observed in your profession, and erroneously transferring them to everyday driving. I think it would be productive if you were open an alternative explanation. I had the (mis)conception that driving build up static and then I get zapped etc., but my observations did not explain that mental model at all. My new realization explains everything and I am quite confident in that. Still willing to be proven wrong but so far I haven't seen any proof. Of course I am not saying that you should go out of you way to prove me wrong, but you are more than welcome to do so. I have been annoyingly pedantic explaining my tests, but that was the only way I saw for clarity.

 

Would you be willing to change your position if you saw that modern car tires are sufficiently conductive? Because that would imply that static does not accumulate. All my tests have shown this to be the case, albeit only on my car and tires.  I am now reading things that support my position:

 

https://community.cartalk.com/t/tire-static-electricity/61591

 

https://forums.anandtech.com/threads/how-is-a-car-grounded-if-the-only-thing-touching-the-ground-are-4-rubber-tires.155569/

 

I have read a few more, but I cannot find them now. Now, as I further further read on this.... Seems like with even newer tires, they add silica (good insulator) and use less of the carbon compound. This apparently increases the tire resistance:

 

http://www.cartalk.com/content/how-does-static-electricity-builds

 

This would of course increase the potential for static build up, but I don't know if it would be to the point that the car would be significantly charged (it may be). I think it would safe to assume that even with the newest tires, the tires are not perfect insulators and indeed ground the car for all practical purposes we are talking about. My tires are 2014 Michelin with middle of the road price-wise. So, while not sure what the composition is, I believe they are conductive and the biggest contributing factor to static is exiting the car.

 

38 minutes ago, Scooby said:

Your car is a giant capacitor when you are driving it.

It might be a capacitor, but it does not mean it is carrying a charge. And this is where we disagree. I am claiming that the tires are grounding the car. This explains all the remedies for the problem, such as the one I described in (5), which is also what is proposed heavily on the internet. So I believe the driver is building up the static as he is sliding out of the car. 

 

I hope you don't come back saying 'whatever' because I'm not pushing back with hostility. I just want to stand my argument as I have been mistaken all along, and my realization has clarified things in my mind. It would be a shame if I was viewed as still being misconceived because I don't believe that to be the case (and want to be sure).

 

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Your car is carrying a charge.

 

The fuel bowswer I mentioned in the thread, we measured the static charge build-up on it. The truck is a vehicle. That is how I know the voltage we measured is well over 80,000 volts.

 

I know tires can conduct, I never said they didn't.

 

As I mentioned, get an anti-static strap.

Edited by Scooby
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On 12/10/2016 at 1:14 AM, habu2 said:

 

It's not the current that stings, it's the voltage.

 

The 'shock' from this kind of static electricity can have very high voltage but is very very low in current.

 

By just rubbing your sweater's arm against your body you can develop over 100,000 volts potential per linear inch of cloth.

 

I've blown a few CPUs while forgetting to wear a static strap on my wrist.  Just one little touch and pop, it's fried.

 

John Hairell  (tpn18@yahoo.com) 

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4 hours ago, Scooby said:

Your car is carrying a charge.

No. I am 100% certain that the car is not carrying a charge that causes a spark at my fingertips. I explained all of it above. Now, if you're going to get into the semantics of 'I told you it is carrying a charge, not how much', don't do that.

 

4 hours ago, Scooby said:

 

The fuel bowswer I mentioned in the thread, we measured the static charge build-up on it. The truck is a vehicle. That is how I know the voltage we measured is well over 80,000 volts.

You are clearly not reading what I have written.

 

4 hours ago, Scooby said:

 

I know tires can conduct, I never said they didn't.

The only way for your argument to make sense is for the tires to be non-conductive.

 

4 hours ago, Scooby said:

 

As I mentioned, get an anti-static strap.

As I mentioned *three times* I am not looking for a solution. I know what the solution is. So feel free to stop the diversion. 

 

I'm looking at the situation from your perspective. If you are going to be so steadfast in your conviction, at least have the courtesy to read what I have written carefully and put some thought into it, or try it for yourself. I am telling you where you are making a mistake and you are still blindly making this erroneous transfer of your experience. If you are still insisting, I can't take you seriously anymore. I am surprised that you can be this dismissive about my observations, especially given that I am clearly articulating what I am experiencing. 

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:rolleyes: that's a sure way of getting the thread.... :lockd:, though you're prolly saying that in a lighthearted way anyway. That aside, despite our differences in this thread, Scooby is a good guy from what I can tell on arc. I'd take him any day over D.T.

 

P.S. Mods, please cut some slack for humor. Promise no trolling here.

Edited by Janissary
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