----- Original Message ----- From: "Bruce Johnson" <[EMAIL PROTECTED]> To: "G-Books" <[EMAIL PROTECTED]> Sent: Monday, February 10, 2003 1:04 PM Subject: Re: magnetized screwdriver bad?
> Everybody needs to find an old, dead hard drive...go get one, I'm sure > there's one laying about somewhere... > > Now disassemble it. > > (for those of you who are junkyard impaired, here's a picture: > > <http://www.guaranteedrecyclingxperts.com/imagebank/parts/hdd/platters.jpg>) > > That metal bit with the number 940430 on it is an assembly with two > very, VERY powerful magnets in it. If you disassemble those you will > find that each one will lift many many pounds. > > One from an average 3 1/2" desktop HDD stuck to the side of my desk will > stick tightly enough to allow me to pull my 230 pound self on a wheeled > chair to my desk rather than disattach from the steel desk. > > Two from a laptop HDD serve is powerful recipe holders on my fridge, > holding about 10 sheets of paper stacked up. > > These are within a few inches of the data on your hard drive as it's > working, all the time. > > NOw...what do you think you have to worry about with a screwdriver that > can barely hold a screw weighing a few milligrams very well? > > -- > Bruce Johnson > University of Arizona > College of Pharmacy > Information Technology Group > > Institutions do not have opinions, merely customs > Basic Computers 101, how is data stored on a Hard Drive? Referring to your supplied picture that little pointy thing setting above the platter has current running through it when the computer wants to write something to the disk when the current goes in one direction it causes a section of the disk beneath it to be magnetically polarized in one direction, switch the current in the other direction it reverses the polarity on the disk. To read the data, the magnetic area of one polarization induces a current in the head in one direction for a "1" and the other for a "0". This is very basic but it's the MOTION of the polarized areas moving under the head that causes the currents to be induced or written. Put a magnet in MOTION over the disc such that the lines of flux pass through it and the data WILL be scrambled. Back in my Navy days we used to erase tapes from our sonar and electronic surveillance using a large electromagnet; set a tape reel on the box turn it on and spin the reel a few times. The key is there has to be relative motion between the media and the magnet. The reason a magnetized tip on a screwdriver "PROBABLY" will not harm a hard drive is that the case serves as a magnetic shield for the disk deflecting the magnetic lines of force away from it. The magnets that control the read/write head have their polarities aligned to each other and as long as their lines of flux don't change in relation to the disk, they won't interfere with it. my $.02 Joe Ellis -- G-Books is sponsored by <http://lowendmac.com/> and... Small Dog Electronics http://www.smalldog.com | Refurbished Drives | -- Check our web site for refurbished PowerBooks | & CDRWs on Sale! | Support Low End Mac <http://lowendmac.com/lists/support.html> G-Books list info: <http://lowendmac.com/lists/g-books.html> --> AOL users, remove "mailto:"; Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive: <http://www.mail-archive.com/g-books%40mail.maclaunch.com/> --------------------------------------------------------------- >The Think Different Store http://www.ThinkDifferentStore.com ---------------------------------------------------------------
