Results 1 to 4 of 4

Thread: Static electricity - Quantity of charge induced.

  1. #1 Static electricity - Quantity of charge induced. 
    New Member
    Join Date
    Nov 2013
    Hi all,
    Let us say I have rubbed cat fur with nylon. Is there any relation for determining the amount of charge (in Coulombs) induced on either of the materials?

    Reply With Quote  


  3. #2  
    Brassica oleracea Strange's Avatar
    Join Date
    Oct 2011
    They will be equal and opposite. Apart from that, I would imagine that there are too many variables to predict anything.

    ei incumbit probatio qui dicit, non qui negat
    Reply With Quote  

  4. #3  
    Join Date
    May 2013
    Quote Originally Posted by Strange View Post
    They will be equal and opposite. Apart from that, I would imagine that there are too many variables to predict anything.
    I do not think I have ever encountered a quantitative relation for the rate of charge separation caused by rubbing insulators together. It seems to be something inherently too difficult to model. I can imagine variables such as air humidity and surface finish may make it a hopeless task, though I do not know this for a fact.

    Or does anyone know of anything that does this?
    Reply With Quote  

  5. #4  
    Forum Professor
    Join Date
    Jan 2013
    Results done in a vacuum are fairly predictable, but still, variables exist with regard to surface qualities. Aside from the materials asked about, smooth, hard surfaces, such as glass, produce the most (I think) predictable and repeatable results. Try searching "Wimshurst" machine, or "static Machines". Here is a reference quote:

    "XXV. A New Form of Influence-Machine.

    In April 1891 I had the honour to submit to this Meeting a very useful form of experimental Influence-machine, by means of which I was able to show that almost every combination of glass and metal, and also that plain glass disks, when moved and suitably touched, were capable of producing a flow of electricity. It is one of those combinations, somewhat modified and extended, which I have now the further pleasure of bringing to your notice. The machine consists of two disks of plate-glass, each of 3 ft. 5 in. diameter and inch thickness, mounted about inch apart on one boss and spindle. This spindle is driven by means of a handle, and the disks rotate in one direction. In the space between the disks are fitted four vertical slips of glass, two being situated on the right-hand side of the machine and two on the left-hand. The vertical edges of the slips which come nearest the spindle are cut to an angle, leaving a rather wider opening at the circumference than at the centre of the disk. Upon each slip is a brush, A, and also an inductor, the brush and the inductor being metallically connected; the brushes are made of fine wire, and touch very lightly on the inner surfaces of the disks. The glass slips slide into place by means of suitable grooves at their top and bottom ends; they may be removed and replaced readily at pleasure. The essential parts are fitted together within a glass case, and in all respects the machine is so constructed as to be useful for experimental work. The limited size of the case causes the insulating distances between part and part to be small, hence the length of the sparks is reduced. All the surfaces are coated with shellac, and when the brushes are new and in proper condition the machine is self-exciting. The charges are not subject to reversal when the terminals are opened beyond the striking distance, for then the whole of the induced charges pass by way of the neutralizing brushes C, C. Another feature is that the neutralizing cur*rent may also be broken without reducing the excitement, but then the charges alternate from positive to negative with each half revolution of the disks."
    Reply With Quote  

Similar Threads

  1. Static Electricity Generator
    By TechGeniusX in forum Physics
    Replies: 17
    Last Post: January 18th, 2013, 05:26 PM
  2. Static electricity(newbie question)
    By AlphaParticle in forum Physics
    Replies: 2
    Last Post: October 16th, 2010, 09:36 PM
  3. Static Electricity
    By sunsheer in forum Electrical and Electronics
    Replies: 4
    Last Post: June 20th, 2009, 10:01 AM
  4. Static electricity on the Moon
    By Everlasting in forum Astronomy & Cosmology
    Replies: 1
    Last Post: May 2nd, 2007, 12:17 AM
  5. Replies: 8
    Last Post: May 14th, 2005, 11:28 PM
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts