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Earthing in automobiles

  1. Dec 4, 2014 #1
    < Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown >

    HEY guys ;
    I want to know the types of EARTHING done in automobile . Anybody having any idea ?
     
    Last edited by a moderator: Dec 4, 2014
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  3. Dec 4, 2014 #2

    phinds

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    If you are talking about grounding, all voltages are measured relative to the negative terminal on the battery and all circuits will be grounded to that level. If you are talking about connecting to Earth ground, it obviously isn't done.
     
  4. Dec 4, 2014 #3
    ya i am talking about grounding . What are different types of grounding / earthing done in automobiles?
     
  5. Dec 4, 2014 #4

    NTW

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    Cars are never grounded before and while refueling. Small planes always are. Perhaps it's a sort of tradition...
     
  6. Dec 4, 2014 #5

    phinds

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    You are talking about Earthing. The OP says he is talking about grounding, but I'm not clear whether it's a language thing or not since I already told him about grounding in cars but he asked again.
     
  7. Dec 4, 2014 #6

    berkeman

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    Since this is a schoolwork question, you *must* show your efforts at trying to answer your question. What have you learned from your reading so far?
     
  8. Dec 4, 2014 #7

    Mark44

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    Some cars in the past had an after-market grounding strap that hung off the car's frame and touched the ground. This was done to minimize shocks from static electricity. This was a nice feature for cars driven in cold, dry conditions where you can get quite a jolt when you first touch the car's body.

    I think it's a language thing, primarily the difference between British English and US English. In manuals for British cars it's common to describe the electrical system as "negative earth" with the same meaning as "negative ground" that would appear for American cars.
     
  9. Dec 4, 2014 #8

    NascentOxygen

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    I always understood that the primary motive behind that conductive rubber strap draining static buildup was to reduce the likelihood of the occupants getting car sick on long journies. It was "one of those things" that apparently worked for some people, so it was said.
     
  10. Dec 4, 2014 #9

    Mark44

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    Maybe that was helpful for some, but AFAIK, the primary reason was to minimize shocks from static electricity.
     
  11. Dec 4, 2014 #10

    NascentOxygen

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    So the scenario would be at the end of a ride the occupants would tumble out then get a zap as they reached to close the doors behind them?

    I manage to accumulate charge by walking around the car park then when I reach for the car door (any car door or any large object) I get zapped. Supermarket shopping is painful---on bad days I get a zap every time I reach for a can of anything, or brush against a passing trolley. The visible spark can reach 1/4 inch. I don't see anyone else jumping when selecting items from the shelves, however.

    I try to remember to discharge to the car body before removing the fuel cap when preparing to fill up.
     
  12. Dec 4, 2014 #11

    berkeman

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    Sounds like a clothing or shoes issue. Do you routinely wear a wool sweater or something? If you are just wearing shorts, a cotton T-shirt and flip-flops, does it still happen?
     
  13. Dec 4, 2014 #12

    NascentOxygen

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    Over the years it's been all different shoes, clothes, stores, and latitudes. The only common factor seems to be me---and the dry winter air. I haven't tried dragging a copper earthing strap tied to my ankle, yet. Maybe I'll give it a go this winter ...
     
  14. Dec 4, 2014 #13

    NTW

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    I remember, too, that those strips were publicized as a way to avoid motion sickness for car passengers, and it was said that they worked by discharging static electricity...
    Anyway, they went out of fashion many years ago...
     
  15. Dec 4, 2014 #14

    Danger

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    That's likely right for shocks entering the car, which I've never actually heard of before. The biggest culprit upon exiting is seat or seat-cover material that you slide over as you turn and stand.

    They never did work for that, but do for the shock situation. Although not generally considered for such, it is also a bit of a safety factor for the same reason that it is with aeroplanes and more importantly helicopters; a static discharge has the potential to ignite fuel fumes while a transfer is being made.
     
  16. Dec 5, 2014 #15

    NTW

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    Thse strips may have discharged static electricity, but they were a passing fad, and were sold as 'motion sickness cure'. They are no longer seen anywhere, and fires while refueling cars are extremely rare. If grounding is still practiced while refueling planes, that's probably due only to the strict rules regulating that activity, rules that don't exist for cars...
     
  17. Dec 5, 2014 #16

    NascentOxygen

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    I saw one earlier this year, fitted to a brand new car. It was such a rare sight that it stood out, and reminded me that such things while once common have gone the same way as white-walled tyres. And fox tails.
     
    Last edited: Dec 5, 2014
  18. Dec 5, 2014 #17
    do you want to know earthing in automobiles only or in electrical equipments as well?
    I can say earthing in automobiles is not actually done for the whole system at once ...I think earthing is done in each part separately....
     
  19. Dec 5, 2014 #18

    CWatters

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    The metal chassis of a car is used to complete electrical circuits to save wire. These days it also saves weight which helps with fuel economy.

    Normally the negative terminal of the battery is connected to the chassis (so called negative earth) but years ago some makes of car had a positive earth system. You had to be extra careful when jump starting a friends car.
     
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