During a charged state of a capacitor (Regardless of the type of capacitor),

  • Simple parallel plate:

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  • Parallel plate with dielectric material in the gap:

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  • Supercapacitor:

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How is the attractive force between the positive and negative charges much stronger than the repulsive forces between them?

When I look at the diagram's above, it seems like there are two forces acting simultaneously, the attractive forces holding the electric field, and the repulsive force between like charges.

When the supercapacitor(for example, but analogues to the rest) discharges, there is a negative ion that is unpaired with a +Q charge, and the repulsive force from the adjacent negative ion causes that unpaird negative ion to float away from the current collector plate to the electrolytic solution.

Every time I look at diagrams of charged capacitors, I can't help but notice two electrostatic forces acting at the same time.


1 Answer 1


Parallel plate capacitors with no material between the plates use the electric field to store energy.

It depends on what the material is between the plates. The simple parallel plate is assuming no dielectric. The electrolyte is a dielectric material which has a high charge density than that of air (or vacuum). This enables one to store more charge in a material with a dielectric than that of air in a simple parallel plate capacitor.

Supercapacitors work on a different principle to increase the amount of charge.

In a supercapacitor, there is no dielectric as such. Instead, both plates are soaked in an electrolyte and separated by a very thin insulator (which might be made of carbon, paper, or plastic). When the plates are charged up, an opposite charge forms on either side of the separator, creating what's called an electric double-layer, maybe just one molecule thick (compared to a dielectric that might range in thickness from a few microns to a millimeter or more in a conventional capacitor). This is why supercapacitors are often referred to as double-layer capacitors, also called electric double-layer capacitors or EDLCs). If you look at the lower diagram in the artwork, you'll see how a supercapacitor resembles two ordinary capacitors side by side.

Source: https://www.explainthatstuff.com/how-supercapacitors-work.html

  • \$\begingroup\$ Capacitors do not store energy in a magnetic field, except parasiticly when charging or discharging. \$\endgroup\$ Jul 3, 2023 at 20:58
  • 1
    \$\begingroup\$ I was under the impression from my EM class that this was so, but it appears I was wrong, the magnetic field is only non zero when the electric field is time varying. physics.stackexchange.com/questions/700074/… I have edited \$\endgroup\$
    – Voltage Spike
    Jul 3, 2023 at 21:37

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