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A flux compression generator creates a very large pulsed current. We know from electromagnetic theory, EM waves come about due to electric currents (or equivalently 'magnetic currents'). We can use the pulse of current from a flux compression generator to generate a EM pulse if we use some appropriate antenna. The 'coil' of the fcm itself can take the role of this antenna, but there are other possible contructions which will work 'better'.

EMP blast or electromagnetic blast can only be caused by a nuclear weapon when it explodes in the atmosphere . EMP blast was the easiest but long way to destroying a country since a direct assault will be resisted by anti-missile defense. The energy extracted from the blast will be converted into electricity which will travel all around the place which the blast happened. The electrical surge is too great for any electrical appliance to resist.

You need to accelerate it to exactly 88 MPH and hit it with 1.21 gigawatts of power.

Just be careful you don't inadvertently cause your mother to fall in love with you and thus erase yourself from existence.