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Car getting struck by lightning

  1. Jun 8, 2014 #1
    As we all know, if a car happens to be struck by lightning its passengers will probably be safe. The usual explanation is that the tires of the car are insulators. The actual reason, as E&M textbooks stress, is that the surface of the car, being a conductor, acts as a Faraday cage.

    My question is, why would anyone think that insulating tires protect cars against lightning strikes? To be concrete, suppose that the surface of the car were made of an insulating material and therefore the car didn't act as a Faraday cage. Is there any reason to think that the insulating tires would protect the car? What's the justification behind this belief?
     
  2. jcsd
  3. Jun 8, 2014 #2
    Are you seriously asking us why some people open their mouths and say things that are clearly wrong? People believe all sort of dumb stuff that they heard somewhere and never took the time to think about. Short answer: Lack of critical thinking.
     
  4. Jun 8, 2014 #3
    I guess what I'm asking is, is there a good reason to believe that insulating tires could protect a car, or is it just bad physics?
     
  5. Jun 8, 2014 #4
    It's just dumb thinking.
     
  6. Jun 8, 2014 #5

    CWatters

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    It's probably based on the idea that wearing rubber boots and gloves may help reduce your chances of dying while working on high voltage equipment. It's not the same though.
     
  7. Jun 8, 2014 #6

    Nugatory

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    People are sometimes sloppy about the difference between protecting the car and protecting the people inside the car.

    The insulating tires do reduce the chances that lightning will strike the car at all... but if the car is hit by lightning, it's the Faraday cage effect that helps protect the passengers from further injury.
     
  8. Jun 8, 2014 #7
    No, the tires offer no protection to the car. The lightning already jumped all the way from the cloud to the car. The extra little jump from the car to ground offers no protection.
     
  9. Jun 8, 2014 #8

    Nugatory

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    You sure of that? I've watched two objects of near equal height and a few tens of meters apart in a lightning storm and the one with the better connection to ground took more lightning strikes.

    I do agree that if the car is sitting by itself with no more attractive target nearby, it's going to be toast, tires or no.
     
  10. Jun 8, 2014 #9
    What do you mean by better connection to the ground? If the object is attached to a metal rod that has been buried deep into the ground and may be even had salts added to the soil and has an radioactive source on its top and a fairly pointy end (I've just described a lightning rod) than yes, you're correct. If the object is connected to the ground by just laying there on the ground than no, no added protection.
     
  11. Jun 8, 2014 #10
    Maybe this is a stupid question, but why would burying the metal rod deep into the ground increase the chance that it gets hit? I thought that lightning rods were buried in the ground so that the charge the rod picks us after a lightning strike can discharge safely into the Earth.
     
  12. Jun 8, 2014 #11

    UltrafastPED

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    Around here it is always raining, often quite heavily, when there is a thunder storm; we get a lot of them at the northern end of "tornado alley".

    It is the rain water that makes everything a conductor, even if it doesn't have roots deep into the ground. OTOH, I've seen several trees struck by lightning - it's quite dramatic! - while growing up on the farm. My father even saw lightning strike the ground at the local high spot, which is not very high around here, but taller than the house, and after the storm passed he found a large chunk of sand that had been turned to a glassy substance; looked like a large carrot with a couple of roots. This soil is from a glacial moraine, and is quite sandy, with little pebbles. Ordinarily you would think that it is a great insulator ... but not during a rain storm!
     
  13. Jun 8, 2014 #12

    berkeman

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    One thing is for sure -- that car's radio is going to be toast, and maybe catch on fire. That nice pointy antenna sticking up in the air will make a nice target for the initial corona discharge.

    I agree with duato that the insulation from the ground (via the [wet] tires) is not really going to help. I also agree that with many car designs, the Faraday cage effect will help to protect the passengers inside some. Not a place I'd like to be, though...
     
  14. Jun 8, 2014 #13

    berkeman

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    Holy cow! This guy even volunteers to do some testing for us...

    https://www.youtube.com/watch?v=ve6XGKZxYxA
     
  15. Jun 8, 2014 #14

    AlephZero

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    If you haven't come across "the hamster" before, he's fairly indestructible, as well as not understanding the concept of "risk".
    https://www.youtube.com/watch?v=rCgbd81BTPE
     
  16. Jun 10, 2014 #15

    OCR

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    http://www.lightningsafety.noaa.gov/myths.htm [Broken]

    http://www.lightningsafety.noaa.gov/

    http://en.wikipedia.org/wiki/Lightning
     
    Last edited by a moderator: May 6, 2017
  17. Jun 10, 2014 #16

    D H

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    Last edited by a moderator: Sep 25, 2014
  18. Dec 20, 2014 #17

    DTM

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    It is often stated that it is a myth that a car's rubber tires help protect the car or occupants from a lightning strike. The fact is, the rubber tires do provide SOME protection and the reason is very important. If the car is struck, of course the metal "cage" around the passengers provide a safe place for them. But anything you can do to increase an objects resistance to ground will minimize the chance of an object being struck in the 1st place. It's often stated that if the lightning can jump hundreds of feet through the air, it can jump the last 6 inches through your tires. But this is a bad argument. The tires do hot have to have such a high resistance that lightning cannot go through them, they only have to have enough resistance so the car is not the lightnings path of least resistance. So a tree 50 feet away my provide an easier path to ground while if the car had steel tires, the car may have provided an easier path.

    This concept is very important. A 1/4" of rubber on your hiking boots soles might be negligible relative to to the millions of volts of a lightning charge, but if it makes you a more resistive path than a nearby tree, they can protect you. ANYTHING you can do to increase your resistance (sit or stand on your pack) can help you in a lightning storm.
     
  19. Dec 20, 2014 #18

    FactChecker

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    That's like the old joke:
    A bear jumps out of a bush and starts chasing two hikers. They both start running for their lives, but then one of them stops to put on his running shoes.
    His friends says, "What are you doing? You can't outrun a bear!"
    His friend replies, "I don't have to outrun the bear; I only have to outrun you!"
     
  20. Dec 20, 2014 #19

    FactChecker

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    It seems that there must be something more. If lightning wants to hit you, it can always hop to the side around your rubber soles. That is less than an inch of air to go through to get to ground, and probably not enough to make it strike somewhere else. It might be that the rubber soles stops a static charge from traveling from the ground to you and attracting the lightning. I can easily imagine the rubber stopping a static charge from building up in you.
     
  21. Dec 20, 2014 #20
    But then again if your feet are wet, you might as well be swimming...
     
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