EMP weapons are detonated in the high atmosphere, theoretically as high as 300 miles above the ground (well above the orbits of most satellites, even). Once detonated, the energy released by these weapons interacts with the Earth’s magnetic field, producing an extremely fast and powerful electromagnetic burst that rushes to the ground at 94% the speed of light, slamming everything on the ground with as much as 50,000 volts per square meter at high amps.
Not surprisingly, such a phenomenon would fry virtually every piece of electronics they touch, as today’s electronics are manufactured with delicate circuitry that simply cannot withstand such extreme voltage ranges.
Instantly taken out of service would be many automobiles, televisions, cell phones, air conditioners, airplanes, radios, military electronics, and many satellites. Even more worryingly, such an attack would also take out the backup generators and control electronics for active nuclear power plants