Well, I'm sure we all know about the Electro Magnetic Pulse devices and their potential usage as weapons of mass destruction via aerial detonation. The idea goes, it would fry all electrical and computer systems. This is fine and I understand the logic behind this conclusion.

My question is, what about all of the electrical and computer equipment which is not connected to the power grid, or any other power source, or otherwise "on" or running in any form whatsoever (in other words, disconnected and grounded, like think of a laptop that is off and disconnected from the battery recharger, or think of a cell phone which was off and not being recharged during the EMP detonation.), what happens to that equipment?

Have we all seen the History Channel (or was that Military Channel?) demonstration of this with a car? How the guy drove under the device with the car, and the car goes dead right as he drives underneath the device? Well, what about all the cars that were parked on the side of the road and not running?

Essentially, will it fry circuit board and electrical systems that are not connected to any power source whatsoever, not storing any power, or if they are storing power, are in a completely OFF mode? It seems to me that just like when a Thunderstorm hits your area, turning off the computer would save the computer from the EMP detonation. I came to this conclusion by reasoning that the electro magnetic pulse would need some conduit to the system to destroy that system; that you could save entire systems and even facilities to provide back up emergency functions and services by simply leaving them off, grounded, and protected from the EMP detonation at the time of detonation. Even if there is no back up system laying in wait, a certain percentage of vehicles, computers, and communications systems would have to be OFF at the time of detonation, providing some post EMP-detonation function of these things. These things are the very targets of the EMP device, and one can quickly come to the idea that a nation could prepare for such an event by having an entire system that shadows or mimics the current communication systems, being kept off and protected, laying in wait for this potential time to occur.

So, is it really that simple?

From my limited understanding, you can imagine an EMP to be a concentrated pulse of energy of sorts. The pulse overloads circuits by giving them too much energy, and it does not matter if the device is off or even has its battery removed. I guess you could even hold a thin piece of wire in the air and get it to burn up.

So you could dismantle everything electrical you own, spread it out on the floor, and instead of it all going in one hit, it all burns out individually. Fun fun!

I can't believe that this is the way it would work, because you'd think this would have some sort of negative effect on the human beings in the affected area?

I mean .. our bodies and blood contain metals, and metals and natural conducters of electricity. What is the difference between a circuit board and the same kinds of metals being in our blood for example?

I know that our metals don't have computer functions but I'd still think something notable would occur to the humans in the affected zone of the EMP blast.

From what I understand youve got to turn off your appliance or vehicle in order for it not to get fried, as demonstrated here in the runaway blockbuster hit, Broken Arrow, with John Travolta:
-Pluckynoonez

This is how I understand it to work. Which would mean you could save an entire system lieing dormant, waiting for such an instance.

[edit on 7/21/2008 by runetang]

I'll add this about EMPs: I have read a bit about China's efforts to develop EMP weapons to annhilate US Naval carrier groups. They've spent quite a bit of time mastering a technique that is going to kill a lot of Americans in the near future when the Pacific becomes an active theater whether it's over Taiwan or Iran or whatever.
From what I remember, they have a satellite or high altitude plane drop an EMP over a US carrier group - a carrier and its supporting protective ships and/or submarines. The EMP activates; most to all of the advanced technology onboard is damaged. The Chicoms will then fire a very large group of high speed missiles roaring just over the water at the carrier group, too many missiles for the group to shoot down. End result: Carnage.
Hope our military finds ways to overcome it, but the Chinese have spent a lot of time and money analyzing our predicted tactics, responses and lots of time spying and stealing untold amounts of information about our military.

[edit on 21-7-2008 by KGBmaster]

The effects of EMP is highly dependent upon the length, conductivity
and electrical resistance of the larger circuits involved and the
inherent fragility of any microcircuits in chips.

ANY long wire becomes an antennae and would be an ideal mechanism
to INDUCT current from the EMP "fluxes" (i.e. fast rise & drop times)
thus ANY circuitry, be it ON OR OFF, if it has NOT been shielded
using a Faraday Cage, or has NOT been grounded out using a
diversion circuit (i.e. Varistor or Capacitor or other spark gap to
convert current to heat or light) WILL FRY...!!!!

And thin microcircuits, due to the fast rise times of an EMP pulse,
will just overload and melt into blobs of useless metal oxides much
like a circuit breaker trips upon over-voltage/over-current situations.

So unless ANY device is shielded using Faraday Cages (which are
notoriously DIFFICULT to build for EMP defence), they are mostly toast
in a large scale EMP attack.

I do understand however, that some PURELY optical-based systems
that switch via photonic means (i.e. Gallium Arsenide photo-circuits) WILL
survive because an EMP pulse will just cause large outputs of light to
be emitted much like noisy TV static for the duration of the pulses
and then return themselves to normal.

However any attached electrical motors or other electrically based switching
gear may be fried if they are unable to take the pulsed current load that
would be put onto them. And the ability to take a pulsed high-current load
caused by an EMP, is dependent upon the diameter, conductivity & resistance
of the cable, the ability of a cable's insulation to absorb the heat load without
burning & short circuiting and the ability of a connecting switch to convert
any over-current into easily radiated heat and not melt or break.

There are at least 50 to 100 variables on even minor circuit designs
to consider when building EMP protection...and the best PROTECTION
from EMP is a totally enclosed and PROPERLY GROUNDED Faraday Cage!

My take on EMP is that it's like an X-Ray, but many times stronger.
Being in the construction industry, allow me to give youse a heads-up; go to your local drywall supply house and buy some lead board. It is drywall with a sheet of lead attached to it that will give some protecton against said effects. Be sure to also procure lead-head nails to attach them with and as they are a little costly you need only buy enough to do a closet.
I'm doing mine in a MBRM closet that won't cost more than a couple of hundred $.
That way when the SHTF, you might be able to save at least a t.v. or radio.
Nobody will be left to broadcast, but you will be able to receive.