Re: Wire length (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: List moderator <mod1@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Tue, 12 Dec 2006 19:14:58 -0700
From: resonance <resonance@xxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Wire length (fwd)



Inductance is good and it's usually excepted than max inductance occurs when 
coil height/dia ratio is 0.9H .  This gives max inductance which provides 
maximum potential from  Vsec = - L x dI/dt.  A very large, short, fat, coil. 
One reason Tesla used a 52 ft. dia for his Col. Springs magnifier coil.

However, this is not the only consideration.  Build a coil this way and it 
will always be arcing to the primary!

A 4.5 to 6.0 to 1.0 height/dia ratio almost always results in a very smooth 
running coil.

Dr. Resonance
----- Original Message ----- 
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Tuesday, December 12, 2006 6:22 PM
Subject: Re: Wire length (fwd)


> Original poster: List moderator <mod1@xxxxxxxxxx>
>
>
>
> ---------- Forwarded message ----------
> Date: Tue, 12 Dec 2006 14:29:42 EST
> From: Mddeming@xxxxxxx
> To: tesla@xxxxxxxxxx
> Subject: Re: Wire length (fwd)
>
>
> Hi Shaun, Jared, et.al.
>
>    IIRC, back in Nov 2002, a paper was posted to the  list which showed 
> that
> for any given length of wire and turns/inch there is  a unique solenoid 
> and a
> unique flat spiral which give maximum inductance  for each configuration.
> While it was an interesting mathematical  derivation, I'm not sure that 
> anyone
> ever found it practical for TC  building. If it's not there any longer, 
> I'll be
> happy to re-post it or send an  off-list copy on request.
>    It is also possible to express power input of a  coil in "equivalent
> standard cartloads of buffalo chips per fortnight" instead  of kilowatts, 
> or the
> surface area of memory chips can be expressed in nanoacres.  Again, 
> interesting
> exercises but it seems no one has recognized their great  theoretical 
> value
> yet. ;^)
>
> Matt D.
>
>
> In a message dated 12/12/06 10:15:32 A.M. Eastern Standard Time,
> tesla@xxxxxxxxxx writes:
>
> Hi :  Shaun
>
>
>
> Most of the coils that my friend Larry and I have built  are multiple
> wavelength. The speed of light and frequency determine the  location of
> voltage and current nodes along the wires  length.
>
>
>
> The Neumann equation can be found in many  electromagnetic textbooks.
>
>
>
> L does depend on geometric  considerations and the equation that you have
> shown is correct (in the  abstract).
>
>
>
> Visualize a long piece of wire being like a wet  noodle. We have a 
> collection
> of jars, and when we place the noodle in a  long skinny jar it coils up
> against the walls of the jar giving us a large  number of turns. (but a 
> low
> inductance) Now we take the wire and place it  in a short jar and it coils 
> up
> to give us far fewer turns then before. But  the inductance is much larger
> then with the skinny  jar.
>
>
>
> L = u (wire length)sqrd / 4pi H
>
>
>
> The  wire length remains constant but the Height of the solenoid has
> decreased  with the short jar. Can you now, see why the inductance is 
> greater
> even  though we have less turns?
>
>
>
> Now there is a practical matter. In  real life a short solenoid departs
> significantly from a uniform magnetic  field, (a condition of the 
> derivation)
> So the inductance is not really as  large as the equations would suggest. 
> But
> is very close to true for long  solenoids where the bulk of the magnetic
> field is uniform.