How EMPs work in movies....

In movies like Matrix, Robocop, Stargate or whatever, they always say something like "turn off all your equipment before your fire the EMP" or "EMP won't destroy electronics that aren't on". This doesn't seem to make sense to me because doesn't EMP induce voltage spikes/currents regardless of whether the conductors in the electronics are currently conducting or not?

Yeah AFIAK that's pretty much fictional. Induce 20v on an input to a CMOS device and it probably won't matter if it's on or off. Well it might make some difference in specific cases but who knows, it might be better off being on. Then the pin's probably being driven by another transistor and is lower impedance. But there's likely to be plenty of other high impedance wires ready to be blown even when it's on.

I think one scifi writer started it and people thought it was a cool plot device. It was integral to the Matrix plot, for example. So they ran with it.

Emp

An EMP WILL distroy all electronics even those that are turned off.......

When I was part of the emergency planing commity (as a radio ham I was local radio operator) we were instucted to place an emergency radio wraped in tin foil in a tin box, and bury it in the garden until the nukes had gone off and then dig it up.............. This was supposed to prevent the EMP from distroying the radio LOL

rigdoctor99 said:

An EMP WILL distroy all electronics even those that are turned off.......

When I was part of the emergency planing commity (as a radio ham I was local radio operator) we were instucted to place an emergency radio wraped in tin foil in a tin box, and bury it in the garden until the nukes had gone off and then dig it up.............. This was supposed to prevent the EMP from distroying the radio LOL

Click to expand...

Haha, I gather it would have helped a bit since it would make a Faraday cage...not a very effective one though...better if it be some thick copper foil...plus let's not forget about the nuke blast lol.

Exactly my point, they gave all this advise and had no idea if it would work LOL........... We were doing an exercise once, and they had to be as real as possable. Well as time and cups of coffee took there toll, I needed to go to the loo, so I asked the senior planing officer were I should go and he said, 'Just go up through the blast door and it is the first on the right.'

And just to make things worse, we ploted a 10 killo-ton blast near to the building we were, so I reported over the radio.....'Arials taken out in that blast, no contact now possable between us' The answer I got was 'Almost finnished exercise, cintinue transmitions'............... What a joke that was, I had many a cup of coffee at the radio club with that one........LOL

Well maybe matrix says that but in stargate they dont say to turn it off to save it. I remember they have a shielded room of some kind that will save the super computers from EMP, but they never say turn it off... just protecting stargates good name

EMP can also affect large metal structures such as wire fences.

So guys please tell me what are these "hardened" components which I've seen mentioned for many years? Is there some process that produces emp resistant components?

Gallium Arsenide has been used in place of silicon for this very purpose. It's also much faster than silicon, but the manufacturing process is WAY more expensive. I do not know exactly how it hardens the system, except maybe the junctions are of much lower resistance and so do not heat up as much with the same energy.

I remember in 1984ish time frame, reading in Byte magazine how TI had just developed a 100Mhz GA processor for NORAD. It was true RISC and ran at a whopping 200MIPS. Very impressive at the time.

I worked as a copier repair tech about 10 years ago and the local air base was part of my service territory.
Once I had asked someone about how that EMP hardening and related protection worked. He said some of the computer systems are in heavily shielded bunker type rooms with thick steel in layers around the inside that is supposed to help shield or deflect the EMP around the systems. The lines going in and out have multiple levels of spike, surge and isolation as well.
No exact details though.

It does make sense that a heavy enough iron box would conduct the magnetic field pulse around the stuff inside it to a great degree and also greatly attenuate the EM fields inside it like a Faraday cage as well.

I would've thought there would also be a backup generator because it's highly likely that the mains will also fail during an EMP event.