Reply
Thread Tools Display Modes
#1
Old 09-17-2005, 08:27 PM
Guest
Join Date: Dec 2002
Location: San Jose, CA
Posts: 1,342
Static electricity charge, arc distance

How much of a static charge would you have after shuffling your feet on the carpet, if it arcs 1/4 inch to a doorknob? 1/8 inch? 1/2 inch?

Understood that the humidity of the air would make a difference, what's the approximate value?

Stimulated partly by this thread in MPSIMS, about a highly dubious report of a static issue.
#2
Old 09-17-2005, 09:09 PM
Charter Member
Join Date: Nov 2001
Posts: 12,684
Quote:
Originally Posted by MaryEFoo
How much of a static charge would you have after shuffling your feet on the carpet, if it arcs 1/4 inch to a doorknob? 1/8 inch? 1/2 inch?

Understood that the humidity of the air would make a difference, what's the approximate value?

Stimulated partly by this thread in MPSIMS, about a highly dubious report of a static issue.
Dry air has a breakdown voltage of about 3 million volt/meter. So for 1/4" (about 6 mm) the answer is 18000 volts.
#3
Old 09-18-2005, 05:56 AM
Guest
Join Date: Mar 1999
Location: IL, USA
Posts: 5,209
- - - I have always heard the general rule "10,000 volts per centimeter" for regular atmospheric air. With humidity and dust and all, it drops lower.
------
- By the by, a typical voltmeter can only accurately measure up to a few hundred volts. Tube-circuit voltmeters can go up to a couple thousand volts. Beyond that you need a calibrated electroscope. Online plans for one: http://amasci.com/electrom/sas51p1.html#Electro
,,,,,,
- And I agree, the story sounds like total BS.
~
#4
Old 09-18-2005, 08:28 AM
Guest
Join Date: Oct 2001
Location: Hyattsville, MD
Posts: 941
Quote:
- - I have always heard the general rule "10,000 volts per centimeter" for regular atmospheric air.
Well I have always heard the general rule "24,000 volts per inch."
#5
Old 09-18-2005, 12:19 PM
Charter Member
Join Date: Nov 2001
Posts: 12,684
The differences in the numbers cited demands some explanation. My 3 million volts/m is for breakdown between flat plates of large extent in dry air. This is an ideal condition that produces the maximum breakdown voltage.

The 10000 volt/inch is a statement of the amount of space to leave between points of different voltage to avoid any chance of arcing in a system that depends upon air for insulation. For example, around the high voltage part of a cathode ray tube circuit.

The 24000 volt/inch number looks like one that does the same thing as above except with a lower safety factor.

My 18000 volt number would be a maximum. The electric field intesity around a sharp point is increased over a that between flat plates so if you point your finger at the door know, breakdown would probably occur at a lower voltage than 18000.

The 40000 volts being bandied about in the other thread isn't unreasonable. The electrical capacitor of the human body can be charged up to pretty high voltages with a relatively small amount of electricity and will hold that charge if you don't go near any conductors.
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 10:08 PM.

Copyright © 2017
Best Topics: cherry tree california snap on deals nickelodeon definition congressional records archive clique names roxy roller lyrics pool ball order chloroform effect 16 parkside lane ld50 sugar diesel clatter grapevine california purple goldilocks adopt a wombat marines gunnery sgt compulsive talking disorder bump start automatic firefighter weed benadryl for pain pigeons coo drowning myself pt cruiser reviews anika name reddit gunnerkrigg cut metal pipe rattlesnake poison tankobon softcover animals orgasms my ruthschris omelette cookie clicker swedish sausage alberti popaj qvc 6x6 landscaping timbers what is a high jury duty number can i call the cops on my roommate for drugs does the navy have military police using e85 in a regular engine gasoline smell in washing machine how to tie a ponytail for guys what is bubblegum flavor how to open a car door that is stuck has an nfl team ever forfeited do you have to sand between coats of polyurethane which artery bleeds out the fastest turktrust elektronik sertifika hizmet android what does toss my salad mean how to remove a sticker from a book how are canned mandarin oranges peeled how long does it take to learn photoshop first you get the money then you get the power then you get the woman the titanic underwater skeletons how far can a helicopter travel mexicans outside home depot find cube root using calculator mexican workers home depot 12vdc to 6vdc converter do i have to fill out the whole ballot pork chops and applesauce humphrey bogart late run movie theaters near me publix vs winn dixie prices from = the shire to = mordor what is the opposite of ethnocentrism? is it illegal to park in front of a mailbox taking classes at community college after graduating remove old toilet seat mice in air ducts how fast does an object have to move to not be seen wet dog smell white people