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Home Q & A Board Science-Related Homework Help Physics
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smmiller223 smmiller223
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11 years ago
And I'm not talking about those in faraday boxes, I'm referring to ones unprotected. Would it make any difference if some were energized while others weren't?
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#1
11 years ago
Which is probably a matter of accident as the ones most likely to survive are the ones that are under the cases of those that die - the cases act as shielding.  Isolated units with little or no shielding that are on are more likely to be wiped out than those in metal cases where the case is grounded and the unit is off at the time.
wrote...
#2
11 years ago
No, anything carrying or has the potential to carry electricity is at risk.  The only possible circuits would be the military ones specifically designed to be "hardened" against an EMP.  Whoever wrote the survivalist version of protecting themselves at the eHow link down there is woefully misinformed.  You can't wrap something in a steel pipe and protect it.

The overcurrent that causes the damage from an EMP is what's called induced current. That means that a very strong external magnetic field passing through the circuit causes a current to flow within it. So the power source is carried in the EMP pulse itself. Basically it temporarily hooks the circuit up to power source that's so large it causes damage.  Grounding it makes no difference, unless you've got a very tiny pulse.

You can destroy a microprocessor with a couple of lengths of Scotch tape being pulled, they're that delicate.

Every circuit in your house would blow in a major burst.  Look at the Starfish Prime upper-atmosphere detonation of July 9, 1962.  It was over 1,000 kilometers from Honolulu, but burnt out an impressive portion of the infrastructure of the Hawaiian islands.

I don't know if you've ever seen a major electrical station.  When a surge occurs that has the potential to damage the facility, there are literally detonation charges that physically separate the lines from the power plant before the facility can overload.  This actually causes a "mini" EMP, blowing out circuits of the power plant itself, which is why when a blackout occurs, they can't just flip the switch and turn the power back on.

So it makes absolutely no difference as to if the wiring is actually carrying electricity or not at the time it is hit with an EMP.  The electromagnetism still creates a massive current that blows out circuits, lines, etc.

I know they've been talking about it recently in movies.  I think I actually heard someone say, "EMP coming, turn off the power!"  I guess that made it cool?  But it was wildly incorrect.

Hope that helps!
wrote...
#3
11 years ago
If they are not in shielded boxes, any modern electronics would be zapped and killed. Energized or not, makes no difference.

The only exception is vacuum tube circuits, they MAY survive.
wrote...
#4
11 years ago
Generally passive circuits would survive - active circuits would be damaged...

A resistor would still be a resistor after an EMP attack...
wrote...
#5
11 years ago
What would "die" in an EMP? Basically, any semiconductor circuit, (that means transistors and other solid state devices), would be at very high risk unless the circuit were specifically designed, (Hardened), to survive an EMP.  It would make little difference if a circuit were energized or not when an EMP hit. The extreme voltage pulse would likely destroy all.

Anything with long wires outdoors, (think power and telephone systems), would pick up HUGE pulses in an EMP, and would likely destroy any equipment connected to those cables.  Wires inside metal pipes, especially underground, would have a good chance of survival... but who puts wires in pipes then buries them?  Not many.

What WOULD survive? Mechanical devices, such as relays, and vacuum tube circuits would have a good change of survival, though nothing is impossible. Vacuum tubes may or may not be destroyed by arcing, and relay contacts could be fused. Optical fibers, such as used by long distance telephone circuits are immune to EMPs.
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DatchileDatchile
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11 years ago
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