[Prev][Next][Index][Thread]

Re: TC Electrostatics (fwd)

> snip
 > (since the chareges follow the electric field by ohms law). Now Richard is
 > asking why does this 1 coulomb per second of charge NOT generate a
 > perceptible electric field around and perpendiclar to the wire axis just
 > as an "electrostatic" charge would.  Is does not in this case because no
 > NET charge is gained by the wire as in the electrostaic case. 1 coulomb
per
 > second goes into the wire as 1 coulomb per second leaves the wire.
 > Therefore there is no NET charge on the wire.
 > 
 > When the circuit is disconnected so that no current flows, the charges
 > can build up on opposite sides of the power supply just like if you
 > were charging  a capacitor. An electric field will also appear (just
 > as in the capacitor) between the oppositely charged wires.
 > 
 > In both of these cases, the charges are just ordinary electrons. In one
 > cae the electrons move but the number of electrons in the wire
 > is exactly balanced by the number of stationary copper ions so there
 > is not net external electric field  - -- in the other case the chargind
current
 > of electrons is transient and simply leaves an excess of electrons as
 > compared to the copper ions in the (-) conductor and a deficit of
electrons
 > on the (+) conductor. The final static condition has an electric field
 > directed from the + to -  charges.
 > 
 > Bottom line is: A coulomb is a coulomb no matter if its moving
 > or not.
 > 
 >> 
 >  -Ed Harris
> Ed,
 
> Thoughtful post, I must cogitate on it a bit.  I will note a nice 
>experiment just performed over the Xmas holidays.
 
 <I took my gaussmeter (FW BEll 700) and my Keithley electrometer and set 
> up a 10 foot loop of wire (broken in the center) and connected it to a 
 >150 watt 10kv DC supply.  With a 1 megohm resistor in the middle of the 
> loop. I noted only about .1 guass mag field (near the limit of 
 >discernment with the meter).  The E-field near the wires was very weak 
 >too (~1^10-11 coulomb).  Next I took a ten meg resistor and the mag field 
>effectively went away.  The E filed tripled around the wires. finally I 
 >installed a 300 megohm resistor and the e field was every where - 10^-5 
 >coulomb near the wire- (nearly an open).  Needless to say the mag field 
 >was just at a vanishing point. 
 
 >It would appear that a macroscopic mag field capable of doing real 
 >pondermotive work and a macroscopic E field capable of doing pondermotive 
> things are 100% mutually exclusive to conductive circuiry.  They just are 
 >not friendly to one another and will only be mutually present in tiny 
>amounts if equally potent. (whatever equally potent will mean to the 
 >pensive mind).  It seems that current, the producer of mag fields and 
 >voltage the producer of E fields are not normally found in a wire 
 together.
 
 >When massive amounts of coulombs of charge are flowing in a wire to a 
 load (amps) they are locked down.  Their work is totally magnetic in 
 >nature.  When potential exists on a wire with little or now coulombic 
 flow.  the entire system, becomes a virtual "equipotential conductor" and 
> the coulombs due to potential are available to do ES things and work.
 
 >Your noting the coulombs being stuffed in the wire and pouring out as 
 they go in is a good anaology for the zero E field result.  It must be 
 >remembered, though, that if the electron is the only bearer of charge 
 then those electrons are not really in motion!  It is just the perception 
 >of their motion that is the coulomb flowing.  I don't believe for one 
 minute that the physical particles are in motion from point A to point B 
>just the effective charge shuttling without the mass being in motion at 
 all.  This leaves the question of disembodied charge open.  Charge seems 
 >to be able to be shuttle about in matter without the attendent motion of 
 the matter that bears that charge.  I believe that only in the electron 
> tubes do we see electrons and their locked down charge in motion.
 
>Richard Hull, TCBOR
 
 Richard,  Ed,

The way it was once explained to me, the electrons don't actually move along
the wire, but rather, they "bump into" each other in some (unknown) manner,
and transfer the charge along the wire in that way.  I don't know if this is
a simplistic (or outdated) description.

John Freau