[Myrddin]

How long would electronics be useless after an EMP attack?

If your electronics item is damaged by EMP, you will have to wait until a replacement can be manufactured. It is toast. It's not a temporary effect. It burns out circuitry inside semiconductor chips.

[butterdezillion]

Thanks. And when something is “shielded” is it the way it was made that shields it, or is there something that can be done to protect already-made electronics?