In chapter 76, Pulse, we see a parking lot, a street, and (the contents of) a building across the street being taken out by an EMP gun. The target was a computer within the building.

This is weirdly mesmerizing until Randy’s startled out of his reverie by a clunk. He looks over to see that the van he’s blocked in wasn’t abandoned after all; it was full of Dwarves, who have now thrown the back doors open to reveal a nest of cables and wires. A couple of the Dwarves are heaving a boxy apparatus up onto the roof of the van. Cables run out of it to another boxy apparatus down below. The apparatus is electrical in nature – and doesn’t appear capable of firing projectiles – so Randy decides not to pay it much attention for the moment.

(...) Just after he whacks the Enter key to send this command in to Tombstone, he hears an electrical buzzing noise from the van that makes his hair stand on end for a moment. He sees a cop in the video window, frozen. Then the screen of his computer goes blank.

Randy looks over toward the old van. The Dwarves are high-fiving each other.

There is a screeching of tires, and the sound of a low-speed collision, out on the street. About a dozen cars have rolled quietly to a stop, and some have been rear-ended by others that are still functioning. The McDonald’s has gone dark. Television technicians are cursing inside their mobile units. Police officers and lawyers are pounding their walkie-talkies and cellphones against their hands. "Pardon me," Randy says to the Dwarves, "but would you gentlemen like to share anything with me?"

"We just took out the whole building," says one of the Dwarves.

"Took it out, in what sense?"

"Nailed it with a big electromagnetic pulse. Fried every chip within range."

‡ "Dwarves" here, is how Randy classified people earlier in the chapter: "Dwarves (steady, productive, surly) and Elves (brilliant in a more ethereal way). Randy, a Dwarf, has begun to realize that his grandfather may have been an Elf. Avi is a Man with a strong Elvish glow about him. Somewhere in the center of this whole thing, presumably, is Gollum."

Would this actually be possible as described?


1 Answer 1


Yes, in theory.

EMP -- electromagnetic pulse -- is, speaking in basic terms, a pulse of energy that generates a powerful current in any conductor (the reasons are more applicable to Physics Stack Exchange than here); since this current is higher than what the relatively delicate electrical pathways in most electronics are capable of conducting, they rather literally burn up -- they're destroyed. While there are ways to protect against such a weapon -- Faraday cages being one way -- overwhelmingly the stuff you have lying around has no such protection built in.

However, there are a lot of factors to consider, chiefly among them is that you have to generate a pulse powerful enough that the current it induces in your target(s) is powerful enough to fry it. While this can easily be done up close (try connecting a 9V battery directly to the unregulated 5V input on an Arduino (no, don't actually do this, unless you want to destroy it)), the energy you put into generating your pulse ends up distributed across the entire area of the pulse. In addition, you have the inherent inefficiency of both the mechanism turning your electrical source into a magnetic pulse, and that in the magnetic pulse being turned into electrical energy again in your target(s). What this means is that while it may not take a lot of energy to fry the typical microchip, to fry every microchip in an area takes considerably more energy, not to mention all the energy that gets "wasted" by flying off in directions (such as up) where there isn't anything to fry anyway!

What this means in practice is that EMP weapons require massive amounts of energy to be effective over even the short range. So while the principles behind this scene are sound, I doubt the power requirements for it could be met with a small box sitting in the back of a van (unless Randy's Dwarves here have discovered cold fusion). A further consideration is whether or not this was a "directed" EMP, or just a spherical burst centered on the Dwarves' device (it's not clear from the scene here); if the former, that's technology that just doesn't exist at all (yet, anyway).

  • Powerful EMPs can be generated using explosives as an energy source, but I don't think a reusable electrical device would work for a whole block. If they have fusion batteries or something, then it'd be fine!
    – Nick
    Commented May 1, 2014 at 15:50
  • @Nick Specifically nuclear explosions I believe, however I assumed (and therefore restricted my answer to) that the OP was only interested in the electrically-generated one that the Dwarves used here. In theory such a device would work, but in practice the power needs are so enormous there's no such thing currently.
    – Kromey
    Commented May 1, 2014 at 15:52
  • 1
    True, fusion batteries or something of similar power density would be required. You could possibly generate an EMP of that size with a ton or so of today's Li-ion batteries, but getting that many good Li-ion cells charged that high and transporting them is hazardous to your health.
    – methuseus
    Commented May 1, 2014 at 16:20
  • 3
    @Kromey - Nuclear explosions only produce EMPs when detonated at high altitude (Earth's magnetic field), but explosively pumped flux compression generators are very real... en.wikipedia.org/wiki/…
    – Nick
    Commented May 1, 2014 at 16:20
  • @Nick Wow! TIL!
    – Kromey
    Commented May 1, 2014 at 16:22

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