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My aim was to create a relatively strong electrostatic field to experiment with biological systems. So, I built a kind of "sandwich" made of a plate of aluminium surrounded by two 4mm plates of isolating material (the first one is plexiglass, and the second seems to be AVS or some kind of polypropylene). The aluminium plate is connected to a HV generator. Notice that both the connecting wire and the aluminium plate are very well isolated, to avoid sparks or sensible ionic current flow by air. The generator was turned on at about 40000V. This generator is very well regulated, and has the + wire connected to the aluminium plate and the GND wire connected to the earth. According to my understanding, since the potential of the aluminium plate is +40000V, an electrostatic field should appear near the "sandwich". But I could hardly detect anything near the sandwich (well, actually there is something but not very strong). But then came the surprise whenever I turned off the HV generator: The AVS (or polypropylene) plate became suddenly "charged", and I could detect a strong electrostatic field. This field even subsisted a long time. The experiment was repeated and yielded to the same results. Notice that turning off the generator does not disconnect the secondary coil of the HV generator from the earth, but only stop the primary current supply, so the aluminium plate remains connected to the earth even after turning off.

How to explain this effect ?

Additional details:

size of the plates and the aluminium: about 20 x 25 cm.

width of the aluminium foil: 0.1mm.

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  • $\begingroup$ Can you publish the measurements of the electric field before and after turning off the generator? $\endgroup$
    – Alex Trounev
    Commented Jan 16, 2019 at 22:26
  • $\begingroup$ The problem is that I don't have a precise measure instrument (and furthermore the measurement depends upon the distance), but I am absolutely certain that at the same distance, the electric field was much much stronger after turn off than before. $\endgroup$
    – MikeTeX
    Commented Jan 17, 2019 at 6:19
  • $\begingroup$ What are the aluminum plate width, length, thickness? In what position relative to the vertical was the plate when the electric field was measured (tested)? $\endgroup$
    – Alex Trounev
    Commented Jan 17, 2019 at 12:09
  • $\begingroup$ It would be more exact to speak about aluminium foil, but I used the term plate for convenience. See the edit regarding the details. $\endgroup$
    – MikeTeX
    Commented Jan 17, 2019 at 12:18
  • $\begingroup$ After turning off, I measured the field in various position, not only whenever the plates are horizontal. Nevertheless, whenever the generator was on, I tested the field only with horizontal plates, due to HV hazards. $\endgroup$
    – MikeTeX
    Commented Jan 17, 2019 at 12:24

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