A Faraday Cage is a device that can protect electronic equipment from external electromagnetic radiation. So they are a popular device used by preppers for EMP survival.

It was invented by Michael Faraday, a prominent scientist from the 19th century. Faraday discovered that a charged electrical conductor exhibited the charge only on its outer surface, The interior surface of the conductor remained unaffected.

The structure of a Faraday cage is made from a metal mesh or screen. Once an external charge is applied, the electrons in the metal get redistributed. In the end, the effect of the external charge is neutralized on the inside of the cage.

Here is an example of the phenomenon. 

Consider a flying airplane struck by lightning. The charge will pass harmlessly over the exterior metal hull of the plane, leaving the passengers and the crew unharmed.

You will find plenty of online guides that will help you to make a DIY Faraday Cage. They are very simple to make with household items.

The good news is, you can also use a microwave oven as a Faraday Cage to safeguard electronic equipment during an EMP strike. The metal walls of the oven keep the users safe from the microwaves generated in it. Likewise, they can keep electronic devices safe from outside electromagnetic pulses.

But remember this: most electronic devices need a charge to operate. In case the grid is down, you won’t have a power supply to charge up a functional device.

All in all, for preppers a Faraday Cage can be an effective first layer of defense against an EMP strike.