What causes electromagnetic pulse?

many things can cause this, because of the definition of an electromagnetic pulse. an EMP is the short burst of a strong magnetic field. this can cause electrical surges- burning electronics, so if u attempt to generate EMPs, protect your electronics with a ferritin cage.

THE FOLOWING IS FOR EDUCATIONAL OR HYPOTHETICAL USE ONLY

some of the ways to generate a powerful emp are impractical. first example- Nuclear weapons. if you detonate a nuclear weapon in the upper atmosphere, the radiation will excite electrons, which will in turn cause magnetic osscilations. im not a nuclear physicist so this may be a little off, but i know this all causes an intense EMP about as big as a city.

some more practical ways to make EMPs are kinda dangerous. in using an explosion, you can push a neodimian magnet rapidly through a coil of wire. this creates a EMP to be emitted from the wire. again this probably isn't practical, cuz y not just blow up the electronic device u want to destroy. this is a weak EMP and should be within a few feet of the device

the final way to do this... and most practical, though not very powerful, is with an electro-magnet.
basically run a burst of electricity through a coil of wire to create a EMP. the higher the voltage, tighter the coils, and the shorter the burst- the better the effect. this is extremely weak, and must almost be in contact with the device to be fried. camera components for the flash wrk well for this. or so I've been told.

all of the above is from research not personal experience