An EMP will destroy any electronic device, like computers, within its blast radius, but it will not destoy electical devices like flashlights. At least that is my understanding.
My questions are: What ‘piece’ is it that electronic devices have that electrical devices don’t that an EMP breaks and why does the EMP break it.
Well, I don’t know much about EMP, but a quick search on howstuffworks.com (not a great source I know, but I didn’t think they were likely to be too far off the mark here,) says that they induce a massive current in electrical conductors. This suggests, to me, that the flashlight would indeed be vulnerable… at least, the bulb could blow out and the batteries might burst.
Hope that helps.
This has been discussed a bunch here. The very short version is that EMP works by inducing a current in all the conductors it encounters. That’s plain old wires, antennas, circuit board traces, lightbulb filaments, and integrated circuit innards.
When a bomb goes off, the intesity of the EMP drops off at the square of the distance. So up close, it’ll fry everything from delicate integrated circuits to heavy duty wires like high tension power lines. As you get further away, the stronger stuff survives and only the weaker stuff gets fried. Eventually you get ar enough away that the EMP is so weak it doesn’t do any damage at all.
A light bulb is designed to absorb a lot of current for its size. That’s how it makes the light. IOW, there’s pretty robust electrical gizmos. So they’re gonna survive at a distance that many similar-sized electronic items won’t
If you were at a distance frm the EMP that fried all your electronics, it’d still be a decent bet that your flashlight survived. Keep moving closer & eventually it won’t survive either.
You could “harden” a computer circuit by encasing it in lead. Your car will have many individual computers in it depending on how sophisticated it is. There may be: a timing pickup, engine computer, transmission computer, brake computer, suspention computer etc… Some cars have 3 computers just for the transmission. Not sure if the wiring has to be shielded.
You don’t need to encase the thing in lead. What you really want is a conductive cage. It doesn’t even need to have solid walls. As far as EMP bursts are concerned, a screen with holes in it is pretty much the same as a solid piece of metal. The cage needs to completely surround the device, and you have to be very careful about adding protection on any wires that go in and out of the cage. Google the term “faraday cage” for lots and lots of details.
And when it comes to car electronics the body of the car itself would be a faraday cage.
A very poor one. You can count on most, if not all, of the electronics in a car getting destroyed by a strong EMP. Shielding isn’t sufficient. Any wires or cables that are connected to an electronics device provide an antenna and a path for the surge to get inside the device and destroy it.
Lead would shield it from particulate radiation, which can wreak havoc in electronics, but how would lead, as opposed to another (better, lighter) conductor, shield electronics from an EMP?
And as far as I know, radiation-hardened circuits are simply designed differently (to e.g. avoid buildups of charge, deal with stray currents safely, have isolated subsystems to prevent discharges from frying the whole chip, require a bigger potential difference than usual to flip bits, have redundant data storage and be robust in detecting errors, etc.), not coated with lead—at least when they’re used on spacecraft. Military hardware could be different, I guess.
Neither of you have this quite right.
The primary cause of the “EMP” is the gamma radiation from the nuclear reaction. Note that gamma radiation is electromagnetic, and not particulate, except in the “photon wave/particle duality” sense. Gamma radiation is most definitely light. But lead shielding would protect against gamma radiation, which isn’t particulate in the sense that I think you (Podkayne) mean it. And at infra-red frequencies, never mind gamma frequencies, none of the materials that we commonly think of as conductors act as conductors any more. Other factors, e.g. nuclear mass, start to dominate.
However, the gamma radiation interacts with electrons in air molecules. The gamma photons get re-emitted at much longer wavelengths (Compton effect). It’s this longer wavelength re-emission that’s commonly referred to as “EMP”.
Yeah, you’re right. I wasn’t thinking about hard EM radiation at all.
Right . . . and that happens long before the radiation (in any form) would hit any lead you coated a circuit with, right? So do they use lead to protect circuits from EMP or any kind of radiation? I’ve googled using Pb instead of lead, because, you know, lead (lĕd) the metal, lead (lēd) as in wire . . . but I can’t find anything.
Considering that lead sports a tenth thickness of around 2" for certain energies of gamma radiation, this might not be the best of solutions for protecting your delicate electronics. Even if the part is miniscule, it would have to be encased in a pretty massive ball of lead in order to properly shield it.
(tenth thickness is the thickness where radiation is reduced to 1/10 of its original strength)
EMP isn’t “any kind of radiation”.
Lead is used to protect circuits close to known X or gamma emitters, e.g. in hospitals and nuclear power plants.
It isn’t used, AFAIK, to protect against EMP, because the EMP problem occurs at much lower frequncies:
So what’s better than two inches of lead? Ten feet of concrete.
I have to correct this. I should’ve said:
And at even higher frequencies, other factors…
Hmmwah? What point are you trying to make?
OK, I’ll rephrase. Lead isn’t used, AFAIK, to shield against EMP. It is used to shield against other, non-EMP radiation. Your question was “So do they use lead to protect circuits from EMP or any kind of radiation?”. The answer is, yes, lead is used to protect circuits from some kinds of radiation, but AFAIK, EMP isn’t one of them.
Okay, thanks.
Related, but possibly stupid, question: Would a bulb in an EMP light up briefly ? Would you be able to track the path of an EMP through the lights in a city or a warehouse of light bulbs ? What other noticable physical effects might there be ?
SD
As a related question how close could a human be to the EMP blast beyond the heat and pressure danger radius. Would the EMP energy component have almost no effect on humans even at the strongest areas of the pulse?
Or, go to the Bible - MIL-STD-461E
Warning: This link goes to a 263 page PDF.