h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Since the weather has turned a lottle colder, I have suplemented my usual cotton tee-shirt round the house wear with thin outdoor sweat shirt type things commonly worn by outdoor types. I have loads of them because they are great for what they do.

However, they are mostly polyester.

I moved into my current house in the spring last year and am not responsible for many of the carpets. I am responsible, however, for replacing most of the light switches with brushed steel ones.

The result is that I am getting a static shock most times I switch a light on or off. Therefore I seem to have a number of choices:-

1. Live in the dark.
2. Live with all my lights on until the spring.
3. Get a new wardrobe.
4. Crank my heating right up and stick with the cotton tee's.
5. Attach a short metal earthing chain to all of my trousers.

And now!

I am starting to get shocks through the paint on my walls where there is a steel former on the corners.

When I can remember, I am carrying a pen around with me so I don't have to touch the switches!

Aaaaaaaaaaaaaaaaargh!

PP

So is there a question in all this?

If you're looking for ways to avoid the shocks - they're most likely due in part to dry air. (I could bore you with a long scientific explanation here, but just believe me that cold air holds less moisture than warm air, in absolute terms.) When you warm the air back up through heating, you need to put moisture back into it. Try generously watering your plants, line-drying your laundry indoors, putting a full kettle on your woodstove (if that's what you're heating with) and leaving it there, or putting shallow bowls of water on your radiator.

Also, don't shuffle. And try slippers with rubber soles.

Hm, sounds grim

I'd put a strap on your trousers... Definitely!

Or - check your wiring

Or - um - I dunno really. good old fashioned wooly jumpers?

This wasn't really a question - more of a whinge. And I guess I was hoping that someone would say that they have the same problem. Then I would have felt less scared of my house. I am beginning to believe that it is out to get me......

I am pretty sure that the wiring is not at fault. I know that the switches are earthed properly and if it was the electrics I don't think that the walls would have joined in! And it started along with the dropping temperature. I haven't even had to change a light bulb.

I have purposly been drying my washing indoors for the last week or so to raise the humidity, but that doesn't seem to have made any difference.

Most of the time I am very happy with my wardrobe, and wasn't one of the experiments that we did at school, to rub a glass rod with a woolly thing?

I'm off to bed. I have earthed the legs.

PP

It happens to us in the office upstairs, where there's laminate flooring. Everywhere else has real wood, cork, or tiles.

PP, I have the same problem, although from Mal's explanation I get that it's the whole bloody environment for me Living in a dry climate, where it's been very windy for months, I can't realistically create more humidity.

I thought it might have been polar fleece I was wearing, but it's been happening with cotton clothes too now. Mostly it's the car or the aluminium sliding front door Can I earth those?


Mal, I would be interested in a scientific explanation if you feel like it. It's actually more humid here than normal, some days are muggy which is weird for here. I'll have to see if the static shocks happen less on those days.

I've been assuming it's also something to do with my body, otherwise it would be affecting everyone (likewise PP's house).

Kea,

where are you? It sounds lovely. I have just come home from my ladyfriend's house in the light snow which will be worse by the morning. And colder!

Hertfordshire, UK.

PP

Hi PP, I'm in the South Island of NZ. It is lovely. Mid summer and we had snow and a frost in the last month

I tend to get static shocks when I close a car door. Usually only when I am wearing trainers. I admit to lingering when travelling with others, so that I am the last one to shut my door. Those shocks hurt!

Perhaps you need to wear cotton or wool socks, Mr Pink P, with leather soled slippers ( presumably it is too cold to go barefoot?) to try to lessen the amount of static that is building up on your body.

Am I right in thinking that the static is an electrical charge built up in your body that then earths itself when you touch something metal? ie in my case a car body.

I used to get it when I got out of a car or when I was shopping (metal trolleys). I fixed it by always making sure I'm holding onto the metal frame of the car before I touch the ground, and by constantly touching the metal of the trolley when shopping. I think it has something to do with dissipating the electrical charge before it can build up to the level where it really hurts. Dunno how we can adapt that idea to your situation. Maybe you could make yourself touch the metal more often, before the static can build up. Or else just touch someone else, that gives them the shock. I don't know if keeping something metallic on your person would help, but it could be worth a try.

Hang on when getting out... getting in, try slapping the roof - for whatever reason, it seems to reduce the shock to nearly nothing - a sharp (but not too hard!) slap.

I believe that it is a static build up in me. This week, I am mostly wearing my walking socks whick are described as "wool fusion". Ah ha! I thought. Wool fusion? Not actually WOOL then. So a bit of research and I find I am walking about on 62% plastic socks. Bingo. I am going to try barefoot.

I had even considered getting married so that I had someone to turn the lights on and off for me.

I used to get the car thing on an old car of mine, I don't remember what it was, and shopping trollies - especially where there is a carpet in the shop. Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaagh!

PP

Right. The scientific explanation.

When you're talking about humidity, you have two measures: absolute (or specific) humidity, which is simply the amount of water in grams currently in a cubic metre of air (at normal pressure etc, because of course a change in pressure will change how much air there is in a single cubic metre of air.)

Relative humidity, given in percent, says how much of the water the air could potentially hold is currently being held by the air. It's the measure you'll find in the weather forecast, because both very high and very low humidity are uncomfortable. Humans like a range of about 30% to 60% - any lower, and we tend to dry out. Any higher, and we start feeling clammy; the water can't evaporate as well, which also means sweating is less effective. That's why muggy days feel hotter than merely hot ones.

But hot air can hold more water than cold air, in absolute terms. (Though that in itself is misleading; the water vapour isn't attached to the air in any way, it just occupies the same space as part of the mixture of gasses.) So when the temperature falls, the relative humidity goes up, until it reaches 100% - that's what we call the dewpoint, when the water starts condensing. It happens even on a very small scale - air in a room isn't uniformly warm - which is why there's condensation on cold surfaces, like a glass full of icy lemonade on a hot day, or the mirror when you get out of the shower.

(It's also the reason you have to wrap a house in a big sheet of plastic if you insulate it on the inside, but that would be going too far now.)

When you warm that air back up - outside air you've brought indoors, for example - its absolute humidity stays the same, but the relative humidity *drops*. You get dry air. So far, so good.

But why does it cause static shocks and frizzy hair? That's a question for the next post, this one's getting too long!

Essentially, it's like this.

Static charges are constantly being built up when you move through, around, and against your environment. Usually, they can dissipate quite quickly, just disappearing back to where they came from. But they'll build up, of course, if there's no way for them to get away. Like when they're surrounded by insulators. Dry air is an excellent insulator; it's the water vapour that will conduct the charges. The plastic handlebar on a shopping cart is also an excellent insulator, that's why the charges on you don't get away until you touch the metal shelf, or your metal car!

Static electricity is simply an imbalance between positive and negative charges, and they don't like that. They'll try to balance out and pair off as quickly as possible once you get them near each other (think typical male and female teenagers!) The same charges, on the other hand, will repel each other - when you rub your hair with a balloon or even just pull a wool sweater over your head, the hairs will all try to be as far away from the others as possible, because they're all carrying the same charge.

Static electricity is also a different form than we're used to, because it's just that, *static*, not a flowing current like what we usually think of as electricity. It's potential energy. And having it resting on you isn't painful in the least. It's the current that's the problem. Pulling a sweater over your head, you can hear the crackle of several hundred volts, but they're mostly harmless.

Electricity will always take the path of least resistance. (Literally, with resistance measured in ohms.) Unfortunately, the path of least resistance is often you, because you're filled with water with salts and minerals dissolved in it - electricity loves that! And so when you, full of negative charges jumping around on your clothes and hair and more than ready to get away from all their pesky relatives touch something that's full of positive charges just waiting to make new acquaintances - BZZZZZZT! That's why you'll give the cat a static shock when you pet it. If you touch something that's a good conductor, like metal, the charges will also use that opportunity to make a run for it!

So the solution is:

1. Make the air moister, so the static charges can go away before they build up.

2. Insulate yourself less - that doesn't mean dress cooler, it means wear things made of materials that aren't such good insulators in an electrical sense, because static electricity is caused by touching two insulators together. So cotton instead of wool or polyanything. Or insulate yourself *more*, by wearing shoes with rubber soles, for example, so that while the charges will build up between the carpet and your soles, they won't travel to you.

3. Don't shuffle. Rubbing increases the surface area by a lot, so it builds up more charges.

4. Ground yourself more often. Don't wait for the charge to build up. You can keep a finger hooked over the metal part of the shopping cart handle, for example. While that doesn't have charges to compensate for yours, it's a big enough piece of metal that they'll be able to find room there more easily than on you.

I'd always wondered why the air was drier on cold days.

Glad those endless Monday mornings in Prof. Voss' lectures were of use to someone, then

Apparently, you can get antistatic hand lotion and even, for those working with electronics a lot, grounded shoes - makes a change from those wristbands, I suppose.

the conversation was too long for me to read through but.... has it occured to anyone to wear gloves?

Imagines Mr Pink P in yellow marigolds...,hmmmm