RE: Piezo HV Power Supply

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Dave,
         Perhaps I can answer this for you:

On 10 Apr 2002, at 21:00, Tesla list wrote:

> Original poster: "David Thomson by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <dave-at-volantis-dot-org>
> 
> Hi Pete,
> 
> Dave T.
> >>Your formula for energy is wrong in that it should be:
> >>joule = farad * volt^2
> 
> Pete K.
> >Your formula for energy is incorrect.  The energy in a cap is:
> >Joules = farads times volts squared divided by two.
> 
> Well, let's take a look at this.
> 
> >From NIST http://physics.nist.gov/cuu/Units/units.html
> 
> Farad = m-2*kg-1*s4*A2
> Volt = m2*kg*s-3*A-1
> 
> Farad * Volt^2 = m-2*kg-1*s4*A2*m2*kg*s-3*A-1*m2*kg*s-3*A-1
> Farad * Volt^2 = s-2*m2*kg
> Farad * Volt^2 = joule
> 
> Where does the "1/2" come in?
> 
> Can you direct me to the source that you referenced?  Perhaps your source is
> wrong?

It isn't. Unfortunately, your argument takes no account of the energy 
required to transfer charge across a potential difference. To arrive 
at the answer requires some simple calculus. Rather than repeating it 
here (sans access to the appropriate symbology), I refer you to the 
exact derivation in "Fundamentals of Electric Waves", 2nd edition by 
H. H. Skilling Ph.D., pub. 1948 by John Wiley & Sons Inc., New York 
and Chapman & Hall Ltd., London.  The relevant pages are 64 and 65. 

Regards,
Malcolm