What are the risks involved if one were to stand between two large conducting plates (i.e area where air acts as the dielectric for these plates) and the capacitor is connected to a large voltage power supply in the following cases:

  1. If the high voltage power supply is DC and applied for a long time and someone suddenly enters between the plates, is there any possibility of getting shocked in the transient state?

  2. If the high voltage power supply is AC then what will be the effect at steady state if someone were standing in between the plates?

I thought that since the plates are electrically isolated due to air, if one were to stand in between the plates, they aren't going to get shocked although there is continuous current flowing through it (but it is due to the change in the electric field which causes induced electric current and the electrons of the air don't participate in current flow.)

I'm not sure whether I'm correct or not .

  • \$\begingroup\$ If it's DC, the main concern is breakdown of the insulation between the two plates (arcing through air and the person), where the exact breakdown voltage depend on various factors. What sort of voltages are you working with, and what's an example of a scenario where this happens? // Just realized 2 is "AC" not "arc" \$\endgroup\$
    – crossroad
    Feb 27, 2021 at 7:35
  • \$\begingroup\$ @syntax It is more of a theoretical question for knowledge purpose but what are the worst possible situations in both cases? \$\endgroup\$
    – user215805
    Feb 27, 2021 at 7:41
  • \$\begingroup\$ If you stand in between the plates, you change the air gap and provide a conducting path as has been explained in the first comment. \$\endgroup\$
    – Solar Mike
    Feb 27, 2021 at 8:16
  • \$\begingroup\$ @Solar Mike but if I'm not physically touched the plates , how does I provide a conducting path? \$\endgroup\$
    – user215805
    Feb 27, 2021 at 8:48
  • \$\begingroup\$ Did you understand the words "you change the air gap"? \$\endgroup\$
    – Solar Mike
    Feb 27, 2021 at 8:49

1 Answer 1


The first danger to consider is the danger of dielectric breakdown, and consequent current through the body between the plates.

If however, that danger were somehow eliminated, the next danger I would consider applies to an alternating electric field. Depending upon frequency and amplitude, a body between two conductive plates with an alternative electric field could cause heating in the body, or unwanted electrical activity in the nervous system.

Heating would not be a problem with a static (non-alternating) electric field. However, effects upon the nervous system might still be present. This is an area of current research (see for example this article). Or just google "nervous activity in high voltage fields" or something similar. I believe that at present, our knowledge of the effects of strong electric fields upon the nervous system is rather sparse.

  • \$\begingroup\$ +1, very detailed answer , why possibility of dielectric breakdown increases as soon as we enter in between of capacitor ,is electric field increases if yes why? \$\endgroup\$
    – user215805
    Mar 14, 2021 at 19:09
  • \$\begingroup\$ A human body has less electrical resistance than air. Adding a conductive body between two plates is not so different from adding a conductive sphere between the plates. It reduces the effective distance the field needs to pass through the air dielectric. With reduced effective distance, the field strength in the air will increase, which increases the likelihood of breakdown and sudden discharge. \$\endgroup\$ Mar 14, 2021 at 19:11
  • \$\begingroup\$ thanks ! Is Sharp edges of human body like finger tips causes even More chances of Electric breakdown? \$\endgroup\$
    – user215805
    Mar 14, 2021 at 19:23
  • \$\begingroup\$ Yes, sharp edges are known to increase the likelihood that corona discharge will be transformed into a sudden spark discharge. Corona discharge is a rather uniform current through a dielectric medium. However, if the discharge causes uneven heating, or uneven ionization, the stability of the corona discharge becomes lost. The instability develops very rapidly into a spark (lightning). \$\endgroup\$ Mar 14, 2021 at 19:28

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