This article is long, but give a very good layman's description of the effects of the various EMP problems.
Let me point out an EMP (ElectroMagnetic Pulse) can have several sources, some natural (the sun and earth weather) and some man-caused (nuclear and non-nuclear explosive devices).
I have a background in teaching Chemistry and Physics and I see a LOT of mis-information about EMP in the print and online media. This article is reasonable accurate in what it says although I cannot vouch for the truth of some of the many links contained in the article. Due diligence is your responsibility. Still a good read for those who care about this threat.
My opinion on preps for EMP:
I think having a "Faraday Cage" for your electronics is a VERY good idea, but they only work if your electronics is INSIDE the cage at the time of the EMP. That implies some discipline on your part to put electronics in the cage between uses and having backup electronics always in cages while you use the primary. That means radios, cell phones and computers. If you have a generator in your home system. it "could" be built into a large Faraday Cage, but the wires leading to your home would still be at risk.
NO- wrapping your electronics in aluminum foil is NOT sufficient...
Finally, your incoming power lines need to have surge protection installed which is designed to resist EMP power levels. That is a topic for another whole article, but it is critical to protecting your electronics (and you) while they are being used.
http://www.futurescience.com/emp.htmlI quote from the article (emphasis is theirs):
"
Nuclear EMP is actually an electromagnetic multi-pulse. The EMP is usually described in terms of 3 components. The
E1 pulse is a very fast pulse that can induce very high voltages in equipment and along electrical wiring and cables.
E1 is the component that destroys computers and communications equipment and is too fast for ordinary lightning protectors (although devices that are fast enough are routinely being produced, but are rarely used in the civilian infrastructure). The
E2 component of the pulse is the easiest to protect against, and has similarities in strength and timing to the electrical pulses produced by lightning."
"The E3 pulse is very different from the E1 and E2 pulses from an EMP. The
E3 component of the pulse is a very slow pulse,
so slow that most people would not use the word "pulse" to describe it. The E3 component lasts tens to hundreds of seconds, and is caused by the nuclear detonation heaving the Earth's magnetic field out of the way, followed by the restoration of the magnetic field to its natural place. The
E3 component has similarities to a geomagnetic storm caused by a very severe solar storm."
"In writings on the Internet, there is nearly always much confusion about the very different aspects of the various components of nuclear EMP. In addition, there is much confusion in distinguishing high-altitude nuclear EMP, non-nuclear EMP weapons and solar geomagnetic storms. There are very large differences among these very different electromagnetic disturbances; although there are many similarities linking solar-caused geomagnetic storms and the E3 component (but not the other components) of high-altitude nuclear EMP. Nearly everything written in popular articles, even in the most respectable publications, jumbles up a nearly incomprehensible mix of information confusing the effects of the E1 and E3 components of electromagnetic pulse. This has been largely responsible for the large number of widely-believed EMP Myths."