Cap values?

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

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

Hi guys! For me it's been a good read (pup list) for over a year now.Thanks 
and keep it coming!
Question The ratings on caps have i  have to assume deal with how fast they 
cycle.Is there simple way to grasp this,say with one saying 500uf and another 
being.015?I find with low voltage caps(700acv) ,when connected to 120ac, the 
cap will charge and dis-charge while remaining connected to 120ac.Remove the 
120ac and the cap might or might not have a charge, why?Sorry if this is 
simple stuff,it's not for me. Thanks
                                                                              
     john in nyc