I got a huge shock from it the other night, blue sparks flew...I was wondering how amny volts if any are generated from static electricity?

You really don't want to know.

http://amasci.com/emotor/zapped.html

When two insulating surfaces are adhered (or rubbed) together, two opposite regions of imbalanced charge appear. When these surfaces are later pulled away from each other, a very strong "electric field" appears between them, and this e-field can raise hair, attract lint, etc. In addition, this e-field is an example of pure voltage, or voltage without current. The strength of this e-field is incredibly large when compared to the voltage of batteries and of common electronic circuitry. It is many thousands of times stronger, sometimes hundreds of thousands of times stronger. Everyday "static electricity" involves immense voltages. The tiniest "static spark" is caused by about 1000 volts. Longer "car door sparks" and "doorknob sparks" can involve as much as 10,000 volts. For more info, see: Measuring the "Static Electricity" on your body also Car-door sparks, electric people. - Same Source, different page
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Posted 9/16/2005 6:56 AM
Static electricity in man's jacket leads to burns

SYDNEY, Australia (AP) — A man shocked authorities after he released so much static electricity from his jacket, he left burn marks in the carpet of a business.

Fire officials in Victoria state said the man, Frank Clewer, had built up at least 30,000 volts of static electricity in his jacket simply by walking around the city of Warrnambool, according to a report by the Australian Broadcasting Corp.

He received his first shock when he walked into a local business Thursday afternoon. "It sounded almost like a firecracker or something like that," Clewer told the ABC. - USAToday.com

The length of the spark is proportional to the voltage. The details depend on the electric breakdown potential of air, which in turn depends on things like humidity and barometric pressure. I recall (offhand, without any references just now) that it's somewhre around 9000 volts/inch.

So even those little sparks between the key and doorknob typically represents thousands of volts, not unusual with static electricity. Of course very little current flows before the charges are neutralized, so those sparks are harmless to people but often fatal to electronic microchips.

Professor, my memory is probably less reliable than yours and I haven't looked it up but, I think 9,000 volts per inch sounds very low. I would have said 10,000 volts for a 1/4 inch gap is more usual. In any case I would add that in addition to microchips that static sparks can be very hazardous in explosive atmospheres like gasoline fumes, etc.

I looked around a bit and discovered the figure is more on the order of 75,000 volts per inch. One experiment resulted in approximately 16,000 volts for a 5 mm gap, which is also close to this figure.

I'm glad Professor brought this up and thanks, kitty, for the fine question.

If memory serves...but it doesn't! There's nothing like being off my almost power of 10 <-- red face.

Kitty, you can't avoid sparks, but you can usually avoid directly zapping your fingers by holding a key or other pointy metal object when you approach the doorknob, car door, etc., where you might expect a spark. Here's the explanation: A spark forms when the electric field strength exceeds a certain threshold (that's the wrong number I gave above). For a given build-up of electrical charge, (A) the electric field strength will increase as the distance between objects decreases (that's why sparks happen just before you touch something) and (B) the field strength is inversely proportional to the radius of curvature of the object (that's why sparks tend to form at the tips of pointy objects). Once the threshold is exceeded, free electrons in the air are accelerated sufficiently to start an avalanche of other electrons, in effect forming a plasma that conducts electricity and radiates light: the spark!

If you've ever seen a Van de Graaf generator (developed for serious physics experiments but also used in fun demonstrations of people's hair standing up, etc.), you may have noticed that they use a large, round, metal electrode polished smooth to maximize the radius of curvature everywhere.

My stereo system used to pop or thump whenever I touched the controls in the winter -- not good for the speakers. I solved the problem by attaching one end of a 10 megohm resister to the metal case of one of the components, with the other end standing free. By first touching the free end of the resister, I discharge my static voltage harmlessly to ground without making a spark -- works like a charm.

Thank you guys for the great info!!!

Professor mentioned, the breakdown potential depends on humidity. You may have noticed that you get more shocks in the winter, this is because it is less humid in the winter (cold air holds less water than hot air).



Now the rest of this, people may just want to skip over, but it's interesting to me...

Breakdown occurs when a few electrons are accelerated by an electric field (the strength of the electric field determines how much energy the electron is given) into atoms or molecules and the collisions break other electrons free. A cascade follows and you end up with a plasma (ionized gas). In the case of a static electricity spark, the electrons get to the other side, equalizing the potential and stopping the process. In the case of some other plasmas, like the ones inside your fluorescent lights, the field is maintained externally so the process continues.

What potential (voltage) is required to start the process (the breakdown potential) depends on several things.

The most obvious is the energy required to remove a single electron from an previously unexcited atom or molecule. This is called the ionization potential.

A less obvious factor, but one important to why humid air has a higher breakdown potential than dry air, is the number of other paths energy can take. Atoms don't have many paths. An electron can collide with an atom and cause it to fly off like a ball on a pool table hit by the cue ball. The energy can also excite electrons - if they excite them enough (greater than the ionization potential), the electrons brak free. Molecules are different. They can vibrate. This is where water comes in. A lot of the energy goes towards these vibrations instead of to the electrons. If you want to get a plasma in wet air, you need to put in extra energy to make up for this. To put in more energy, you use a higher potential.