Re: Can you please explain in detail how sparks are formed

Sorry, but there are not any formulae that I know of or could locate.  
Everything seems to be developed on the basis of empirical knowledge or 
experiment.  For some help, including extensive tables, please try the 
Handbook of Chemistry and Physics.  As far as energy required, you can 
high-energy sparks or low-energy sparks under what look like the same 
atmospheric conditions.  One very rough rule of thumb is that you need 1KV 
per mm to get arcing with pointed electrodes in air, but that varies too.  
Sorry that I don't have a better answer.