well not to help you along this path of destruction
Bu tthe US looked into EMP and came up with a working one-shot method. They tehn revised to get a re-usable way
A nuke is the only really way to develop a EMP. The other way is to charge up some caps and short into an inductor (similar to what grrr_arrghh stated), however, that method will only develop narrow-band and of low freq EMP - the damage comes from the wide range of freq and alot of POWER
The one-shot was a massive coil inductor and a copper pipe as the former.
They charge up a massive bank (and I mean massive) of capacitors and then short them into the inductor (similar to what grrr_arrghh stated). However, what was missing was the explosion., timed to the inductor shorting out is exposives along the inside of the copper pipe that then cascade detonate down the pipe, this causes the pipe to expand and shorts out the inductor turns,(in stages since the exposion is a kinda cascade effect down hte pipe). With the decreasing inductor you get a wider freq of EM and also more power.
I had the link to this, ill find again but at work and if I start looking for that kinda stuff im gonna be on the doll. Will find the link at home later