Physics Help Forum Electric field in conductive solutions

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 Sep 5th 2018, 05:36 AM #1 Junior Member   Join Date: Sep 2018 Posts: 5 Electric field in conductive solutions Goodmorning everyone, i'm knew to the forum (so please excuse me if i make obvious mistake) and i mainly joined in the hope to find some help with a question that i have on electric field. Due to some experiment i'm doing i found my self looking for some theoretical prediction of the electric field (E) found inside liquid solutions (mainly deionized water and NaCl). In my experiment I have a rectangular vessel, with two metal electrodes on two opposite walls (the other walls are made of glass). I impose a pulsed positive high voltage potential (+1kV) on one of the electrodes while the other is grounded. In the middle of the vessel is found an empty cilinder with dielectric PE wall. My question is: what should be the E field inside the cilinder? How should it vary with the conductivity of teh solution? I know that for highly conductive material the E should be zero as that inside perfectly dielectric water it should be proportional to the water relative permittivity. As that increasing the conductivity the current flowing through the liquid would increase too. Anyway, i could not find substantial litterature on this topic or for this specific configuration. Thanking in advance anyone who could provide me some hint or good reference. Best regards Attached Thumbnails
Sep 5th 2018, 08:32 AM   #2
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 (mainly deionized water and NaCl).
Isn't that a contradiction in terms?

 Sep 5th 2018, 08:40 AM #3 Junior Member   Join Date: Sep 2018 Posts: 5 Sorry but i don't see why. Deionized water and pure NaCl are the two elements used to prepare the solution. This dosen't imply that the final solution will be deionized (most certanly not).
 Sep 5th 2018, 09:28 AM #4 Senior Member     Join Date: Jun 2016 Location: England Posts: 961 I note that you specify a pulsed supply. So the field you are creating is continually being established, then released. __________________ ~\o/~
Sep 5th 2018, 10:21 AM   #5
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 Originally Posted by Aghi Sorry but i don't see why. Deionized water and pure NaCl are the two elements used to prepare the solution. This dosen't imply that the final solution will be deionized (most certanly not).
OK so you use deionised water to try to get a pure an NaCl solution as you can.

Thank you for that clarification.

Neither of these compounds are elements.

 In my experiment I have a rectangular vessel, with two metal electrodes on two opposite walls (the other walls are made of glass). I impose a pulsed positive high voltage potential (+1kV) on one of the electrodes while the other is grounded. In the middle of the vessel is found an empty cilinder with dielectric PE wall.
What do you mean " the other is grounded" ?

What is the other terminal of your supply connected to?

I think English is not your first language (though it is good), so please be prepared for a bit of discussion to establish exactly what your set up is like.

Sep 5th 2018, 05:23 PM   #6
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 Originally Posted by Aghi My question is: what should be the E field inside the cilinder? How should it vary with the conductivity of teh solution? I know that for highly conductive material the E should be zero ....
I think in this case salt solution, even low concentration , can be regarded as high conductivity , relative to air and PE (polyethylene)

Sep 6th 2018, 01:15 AM   #7
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 Originally Posted by studiot What do you mean " the other is grounded" ? What is the other terminal of your supply connected to?
The other electrode is connected to the ground through a copper cable.
There is no other terminal coming out of the power supply but i'm quite sure internally it is connected to the ground.

 Originally Posted by studiot I think English is not your first language (though it is good), so please be prepared for a bit of discussion to establish exactly what your set up is like. Getting the correct terms may help you in the future.
Ok, no problem. Thank you for all the correction by the way.

Sep 6th 2018, 01:16 AM   #8
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 Originally Posted by Woody I note that you specify a pulsed supply. So the field you are creating is continually being established, then released.
Yes exactly. The repetition frequency of the pulses is 1 kHz.

Sep 6th 2018, 01:18 AM   #9
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 Originally Posted by oz93666 I think in this case salt solution, even low concentration , can be regarded as high conductivity , relative to air and PE (polyethylene)
In a first approximation yes, but what i'm looking for is to discerne between liquids with different conductivity. I also have solutions with conductivity as low as 5 uS/cm that is several orders of magnitude lower than standard tap water for example.

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