large capacitors [was: IBM 029 progress]
caveguy at sbcglobal.net
Thu Jun 11 08:57:13 CDT 2009
On Wed, 10 Jun 2009 21:44:07 -0500, Jim Battle wrote:
>> Not really. For a given technology, the volume is roughly linearly
>> related to the product of the capacitance and voltage.
>That doesn't make sense. energy = 1/2 * C * V^2. You are saying if you
>double the size of the cap you can handle double the voltage, but that
>means four times the energy. That isn't right. It is the stored energy
>that is linear with the size of the cap (roughly).
>I agree that you can double the capacitance if you double the volume,
>which means doubling the stored energy. Great. This is demonstrated by
>wiring two "x" farad caps in parallel.
>But if you wire them in series so they can handle twice the voltage, the
>capacitance is also cut in half. E = 1/2 * (1/2 C) * (2V)^2, which
>works out to double the 1/2*C*V^2.
Peek working voltage is determined by the strength of the dielectric not the surface area of the plates.
The thinner the dialetic (insolator) the greater the Capacitance with a resulting lowering of the max working
voltage given the reduced insilation.
The other factor for determing the the working voltage is the amount of heat generated from leakage due to
internal resistance, which is also directly related to the insulator used ans its thickness. The leakage
current for a given dielectric goes up with the voltage. I=E/R Tells us given a fixed leakage as the voltage
goes up so does the current, so if both the I and the E both go up then the power (watts to be dissipated)
has noware to go but in the form of heat. Often with a big bang if the overvoltage or the breakdown of the
dialetic are extream.
Using activated carbon or better yet nano tubes as plates and an unspecified molecularily thin super
insolator, we double-layer supercapacitors measured in Farads the size of your thumb.
The semiconductor industery showed us how by making the insolation layer very, very thin we could bulid
on chip capacitors with microscopic plate areas.
So given the previous examples in this thread are we talking, waxpaper and aluminum foil, silver plated
mica, oil filed, or super-capacitors ?
The other Bob
More information about the cctalk