I need some help with anyone that is knowledgeable in this area. I have a desktop machine that has about 4tb of data in it spanned across 4 HDs. The drives are in fairly close proximity to each other. I need help designing a home made electro magnet that is directional and large enough that when i flip a switch (or two) all four drives get erased. What i need to know specifically is how large to make the magnets to guarantee 100% data corruption. This is for a computer hardware class that I'm in and most of my classmates think it's not possible and only a thing of movies. Thanks for the help!