super capacitor with small spacing

[Paul]

Hi

From our physics textbook, the capacitance is inversely proportional
to spacing between the 2 plates. what's to prevent us from making the
spacing very small and hence very high capacitance? Coupled with an
inductor, one can make a AC battery out of it. Will too small a
spacing cause a leakage and hence unpredictatible discharge? Thanks

 

[Michael A. Covington]

That is exactly how large capacitors are made.

Medium-capacitance capacitors (e.g., 0.1 uF) have many thin layers of
metallized plastic film, very close together.

Large ones (e.g., 1000 uF) use an electrolytic process to make conductive
layers that are insulated from each other and yet very, very close together.

A coil and capacitor don't work as an AC battery because of resistance. (No
capacitor or inductor has zero resistance.) But a large capacitor can work
as a DC battery; for example, that's how HP calculators retain their
programming while you are changing the batteries.

 

[Tim Wescott]

Hi

From our physics textbook, the capacitance is inversely proportional
to spacing between the 2 plates. what's to prevent us from making the
spacing very small and hence very high capacitance? Coupled with an
inductor, one can make a AC battery out of it. Will too small a
spacing cause a leakage and hence unpredictatible discharge? Thanks

Dielectric strength of any given material is is in volts/meter, so as
you make the material thinner the voltage that the capacitor can
withstand goes down. You can see this in electrolytic capacitors, where
for a given size of case the capacitance diminishes as the voltage
rating goes down. In fact, I've noticed that for a given size of case
the capacitance is roughly inversely proportional to the square of the
voltage rating, indicating that you can store so much energy in the
given volume, and no more.

 

[William P.N. Smith]

Will too small a
spacing cause a leakage

No, it'll cause arcing, and immediate discharge.

 

[Watson A.Name - \Watt Sun, the Dark Remover\]

Dielectric strength of any given material is is in volts/meter, so as
you make the material thinner the voltage that the capacitor can
withstand goes down. You can see this in electrolytic capacitors, where
for a given size of case the capacitance diminishes as the voltage
rating goes down.

I think you got that backwards. At least that's the way it sounds, from
the following.