Question on Transformers

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <TeraJoule-at-aol-dot-com>

Hello.  

    I am new to coiling, and I am looking to build a small coil first.  I 
looked to my high school physics department today.  They have an unlabeled 
transformer that takes D.C. and makes it A.C.  I put 7 volts at 3 amps into 
it and the resulting voltage was able to jump a 1cm-2cm air gap.  I am 
assuming it produces over 3,000 volts because of the dielectric break-down of 
air.  My problem lies in the fact that I do not know the cycles per second or 
even the exact voltage it produces.  I was wondering if perhaps there were a 
few assumptions I could make to determine the capacitor size I would need for 
the TC.  Thank you very much for your time.

~Alex