A wire that is subjected to a magnetic field will generate an electrical current. Where the damage comes in is when the current becomes sufficiently strong enough to burn out a delicate part of the whole circuit. The battery isn't the problem. In todays electronics there are many components that can VERY EASILY damaged by minute voltage spikes and surges. Any metal container that will conduct electricity will protect said circuit be it a radio, ipod or anything else so long as it is completely opaque to the electrical/magnetic wave. It works by directing the charge around the item. The item must be insulated from the container itself.

Good advice from JAB again. One more note, there is no need to ground your Faraday cage. There has been some good discussion on this subject in the thread : http://internationalpreppersnetwork.net/viewtopic.php?f=73&t=792&p=24867&hilit=faraday+cage#p24867

A way to visualize it is as if you are in a submarine under the sea. You are the device you wish to protect. The submarine is the faraday cage and the water is the electric field you are protected from.

there is thought that even a broken circuit might NOT stop the current, it could jump the gap, or it might shoot flames to the house.

house fires are a very real threat from an EMP.

there has been discussions about how to stop this from hitting your house fully.

1) shut off all breakers, and the main breaker.
2) remove your meter!
3) unplug everything!
4) have " whole house surge protection"
5) cut main power line entering your house (i'm not a lawyer, but i bet this comes with consequences!)
6) use EMP outlets for anything that needs plugged in. (see diagram on last page ) http://www.arrl.org/files/file/Technology/tis/info/pdf/118630.pdf
7) when wiring a new house, but a lot of Z and S in the wire, EMP currents move very fast, they don't turn corners well.

that's all i got off the top of my head going to bed. . .

Entropy those links combine EMP with lightening. You are correct when you sais "even a broken circuit might NOT stop the current". Voltages and currents associated with lightening will jump most switches in equipment. They cannot jump if the equipment is not plugged in. However a true EMP induces a current in anything that conducts electricity i.e. anything within the field of the EMP including unplugged equipment. The only way to protect equipment from a true EMP is to have it safely contained in a Faraday cage.

EMP affects mostly LONG runs of wire, shorter runs of wire may or may not be affected. so having things unplugged does give it some protection, but it's not garenteed.

and the one silver lining in all this, is that even the experts that work with these in the US gov't have some facts, and a lot of theory, sometimes that facts aren't facts. . . because there are blips in what is true and then it sometimes doesn't work that way.

i treat everything as theory and i have some people that i trust. . . and the advice i give comes from trusted sources.

An EMP is like a Nova radio wave, and yes the longer the metal, the more radio wave (energy) will be received. Anything that receives a transmission to operate, will be affected. When I was in the military, I was helping to setup a HQ communication site. The Sig's guys were told not to broadcast above a certain signal strength in that area. In the middle of the night, one of them did just to see what would happen. At full power, he broadcasted...every fluorescent light lit up within 500 yards, those within 50 yards blew up. Radio waves are transmitted energy. Those with pace makers know what I'm talking about, they fear micro wave ovens and high amplitude transmissions, like power lines.