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Electrostatic field question

Started by Lamont Cranston ●August 26, 2023
  Assuming two concentric tubes, both conductors with a field between them.
Does introducing a plastic, say nylon in the field change it in any way?
 Direction? Field strength?

                     Thanks, Mikek
Reply by boB ●August 26, 20232023-08-26
On Sat, 26 Aug 2023 12:12:37 -0700 (PDT), Lamont Cranston
<amdx62@gmail.com> wrote:


>  Assuming two concentric tubes, both conductors with a field between them.
>Does introducing a plastic, say nylon in the field change it in any way?
> Direction? Field strength?
>
>                     Thanks, Mikek



Sure.  Just like a piece of coaxial cable, the dielectric constant or
permittivity will change the characteristic impedance and propagation
delay.

Or, if you like, the material will change the capacitance between
them.

boB
Reply by Lamont Cranston ●August 26, 20232023-08-26
On Saturday, August 26, 2023 at 2:34:00&#8239;PM UTC-5, boB wrote:


> Sure. Just like a piece of coaxial cable, the dielectric constant or 
> permittivity will change the characteristic impedance and propagation 
> delay. 
> 
> Or, if you like, the material will change the capacitance between 
> them. 
> 
> boB


  Sorry that does help me understand. This is goes back to the two insulated plate electrodes
with an emulsion between them. I want to know, if I introduce a plastic sleeve over part or all 
of of one of the electrodes, do I still have the same V/cm treating my emulsion?
                        Thanks, Mikek
Reply by Joe Gwinn ●August 26, 20232023-08-26
On Sat, 26 Aug 2023 12:49:29 -0700 (PDT), Lamont Cranston
<amdx62@gmail.com> wrote:


>On Saturday, August 26, 2023 at 2:34:00?PM UTC-5, boB wrote:
>
>> Sure. Just like a piece of coaxial cable, the dielectric constant or 
>> permittivity will change the characteristic impedance and propagation 
>> delay. 
>> 
>> Or, if you like, the material will change the capacitance between 
>> them. 
>> 
>> boB
>
>  Sorry that does [not] help me understand. This is goes back to the two insulated plate electrodes
>with an emulsion between them. I want to know, if I introduce a plastic sleeve over part or all 
>of of one of the electrodes, do I still have the same V/cm treating my emulsion?


No.

.<https://www.youtube.com/watch?v=BXczXJNQvWs>

Joe Gwinn
Reply by Lamont Cranston ●August 26, 20232023-08-26
On Saturday, August 26, 2023 at 2:59:01&#8239;PM UTC-5, Joe Gwinn wrote:


> > Sorry that does [not] help me understand. This is goes back to the two insulated plate electrodes
> >with an emulsion between them. I want to know, if I introduce a plastic sleeve over part or all 
> >of of one of the electrodes, do I still have the same V/cm treating my emulsion?



> No. 
> 
> .<https://www.youtube.com/watch?v=BXczXJNQvWs> 
> 
> Joe Gwinn


 Hmm, I think that helped. At least now, I realize my emulsion dielectric constant is 50 &plusmn; and any plastic 
I would use, has a much lower dielectric constant and is much thinner. I think the effect will be a non issue.
                                  Thanks for the input,  Mikek
Reply by John Larkin ●August 26, 20232023-08-26
On Sat, 26 Aug 2023 12:49:29 -0700 (PDT), Lamont Cranston
<amdx62@gmail.com> wrote:


>On Saturday, August 26, 2023 at 2:34:00?PM UTC-5, boB wrote:
>
>> Sure. Just like a piece of coaxial cable, the dielectric constant or 
>> permittivity will change the characteristic impedance and propagation 
>> delay. 
>> 
>> Or, if you like, the material will change the capacitance between 
>> them. 
>> 
>> boB
>
>  Sorry that does help me understand. This is goes back to the two insulated plate electrodes
>with an emulsion between them. I want to know, if I introduce a plastic sleeve over part or all 
>of of one of the electrodes, do I still have the same V/cm treating my emulsion?
>                        Thanks, Mikek


It depends on the relative dielectric constants of the plastic and of
the emulsion. If the plastic Kd is lower, the field gradient in the
emulsion will decrease. 

What's the dielectric constant of the emulsion? I'd expect it to be
pretty high. Water is 78, and most plastics will be single digits.

If the emulsion is conductive, which it probably is, adding plastic
will further decrease the field in the emulsion. Maybe drastically.
Reply by whit3rd ●August 26, 20232023-08-26
On Saturday, August 26, 2023 at 12:49:34&#8239;PM UTC-7, Lamont Cranston wrote:

> On Saturday, August 26, 2023 at 2:34:00&#8239;PM UTC-5, boB wrote: 
> 
> > Sure. Just like a piece of coaxial cable, the dielectric constant or 
> > permittivity will change the characteristic impedance and propagation 
> > delay. 
> > 
> > Or, if you like, the material will change the capacitance between 
> > them. 
> > 
> > boB
> Sorry that does help me understand. This is goes back to the two insulated plate electrodes 
> with an emulsion between them. I want to know, if I introduce a plastic sleeve over part or all 
> of of one of the electrodes, do I still have the same V/cm treating my emulsion? 


Yes, kinda.   The volts dropped in the plastic can be different from the (gas, liquid) fill, if
the dielectric constants mismatch.   In the extreme case of very high dielectric constant,
it's the same as changing a metal electrode diameter.   In the extreme case of very low
dielectric constant, it's a match for vacuum.
Reply by boB ●August 26, 20232023-08-26
On Sat, 26 Aug 2023 14:55:41 -0700 (PDT), whit3rd <whit3rd@gmail.com>
wrote:


>On Saturday, August 26, 2023 at 12:49:34?PM UTC-7, Lamont Cranston wrote:
>> On Saturday, August 26, 2023 at 2:34:00?PM UTC-5, boB wrote: 
>> 
>> > Sure. Just like a piece of coaxial cable, the dielectric constant or 
>> > permittivity will change the characteristic impedance and propagation 
>> > delay. 
>> > 
>> > Or, if you like, the material will change the capacitance between 
>> > them. 
>> > 
>> > boB
>> Sorry that does help me understand. This is goes back to the two insulated plate electrodes 
>> with an emulsion between them. I want to know, if I introduce a plastic sleeve over part or all 
>> of of one of the electrodes, do I still have the same V/cm treating my emulsion? 
>
>Yes, kinda.   The volts dropped in the plastic can be different from the (gas, liquid) fill, if
>the dielectric constants mismatch.   In the extreme case of very high dielectric constant,
>it's the same as changing a metal electrode diameter.   In the extreme case of very low
>dielectric constant, it's a match for vacuum.



OK, I see I think.

If the dielectric is between the two concentrics, then it will change
things.   But if it is around the whole thing, then not so much.

Does that sound right ?

boB
Reply by whit3rd ●August 26, 20232023-08-26
On Saturday, August 26, 2023 at 3:03:55&#8239;PM UTC-7, boB wrote:

> On Sat, 26 Aug 2023 14:55:41 -0700 (PDT), whit3rd <whi...@gmail.com> 
> wrote: 
> 
> >On Saturday, August 26, 2023 at 12:49:34?PM UTC-7, Lamont Cranston wrote:



> >> ...I want to know, if I introduce a plastic sleeve over part or all 
> >> of of one of the electrodes, do I still have the same V/cm treating my emulsion? 
> > 
> >Yes, kinda. The volts dropped in the plastic can be different from the (gas, liquid) fill, if 
> >the dielectric constants mismatch. In the extreme case of very high dielectric constant, 
> >it's the same as changing a metal electrode diameter. In the extreme case of very low 
> >dielectric constant, it's a match for vacuum.
> OK, I see I think. 
> 
> If the dielectric is between the two concentrics, then it will change 
> things. But if it is around the whole thing, then not so much. 
> 
> Does that sound right ? 


Well, no; the issue is that the dielectric has (resistive and capacitive) conductivity,
and is in series with the (resistive and capacitive) conductivity of the emulsion.
It's a voltage divider, with a voltage ratio that depends on the unknown emulsion as much
as the (presumably known) dielectric.   The "V/cm" measure, though, can remain
constant, if the emulsion and dielectric are matching materials; you've
changed both the "V" and the "cm" parts by displacing emulsion with
the dielectric.
Reply by Lamont Cranston ●August 26, 20232023-08-26
On Saturday, August 26, 2023 at 7:07:54&#8239;PM UTC-5, whit3rd wrote:


> Well, no; the issue is that the dielectric has (resistive and capacitive) conductivity, 
> and is in series with the (resistive and capacitive) conductivity of the emulsion. 
> It's a voltage divider, with a voltage ratio that depends on the unknown emulsion as much 
> as the (presumably known) dielectric. The "V/cm" measure, though, can remain 
> constant, if the emulsion and dielectric are matching materials; you've 
> changed both the "V" and the "cm" parts by displacing emulsion with 
> the dielectric.


 That is a description that I understand.  I seems like a non problem, I have good test results at
800V/cm to 3000V/cm and can go higher if needed. There is also the possibility that lower voltage
are viable.
                                         Thanks, Mikek