What are the magnets on the side of the iPad for?

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Intrepid DIY repair advocate iFixit has given both the iPad 2 and its matching Smart Cover a full disassembly. While the iPad 2 itself contains few surprises inside, both it and the Smart Cover contain 31 magnets in total.

The iPad 2 teardown revealed an internal architecture mostly unchanged from the original iPad. The aluminum unibody has been redesigned to be flatter and thinner than the original, which required a bit of component rearrangement. The A5 processor, which replaces the previous model's A4, is new, but touch controllers and WiFi/Bluetooth modules remain the same.

The main changes include the addition of front and rear camera hardware, which appear to have been pulled over from the iPod touch. An STMicroelectronics gyroscopethe same one found in the iPhone 4 and fourth-gen iPod touch, now accompanies the accelerometer. Tiny rear-facing speakers have replaced the ported speakers of the original iPad.

The LCD panel and the front glass cover have both been reduced in thickness and hence weight, accounting for a large part of the weight difference between generations. Apple opted to glue the front glass on, similar to the iPod touch, instead of using clips like the first-gen iPad. The move reduces repairability, but meant Apple could shave a millimeter or two off all three of the iPads' dimensions. iFixit noted that the thinner glass used in the iPad 2 could possibly be less durable than the original's thicker glass.

Apple also changed the battery configuration from 2 thicker cells to three thinner cells. The total capacity is 25 watt-hours, up ever so slightly from 24.8Whr of the original. Combined with nearly identical electronic components, the iPad 2 is able to achieve the same 10-hour battery life rating.

One internal change that has nothing to do with the iPad 2's performance, however, is the addition of 10 magnets along the sides of the device. These magnets have everything to do with its new Smart Cover accessory, which itself contains 21 magnets. iFixit discovered a couple interesting aspects of the different arrays in both the iPad 2 and its matching Smart Cover.

There are six magnets along the left side of the iPad, arranged in two arrays of one long magnet paired with two shorter magnets. One array is positive-negative-positive poles, while the other is negative-positive-negative. Complementary-poled magnets are in the hinge of the Smart Cover, which is why it only attaches on the left-hand side, andautomaticallysnaps into the right spot.

There are also four magnets along the right side of the iPad 2's front bezel, where the Smart Cover closes. However, there are 12 corresponding magnets in the Smart Cover. iFixit noted that the additional magnets are needed to fold the Smart Cover up and hold on to the steel plate in the last segment of the cover, forming a triangle that morphs into a stand for the iPad 2.

"We were curious to find out whether Apple was using cutting-edge magnets with special properties, such as the awesome correlated magnets we keep hearing rumors about from our über-geek friends," iFixit's Miroslav Djuric said via e-mail. "Sadly, none of the 31 magnets inside the devices had any special properties. All of them were the standard, two-pole kind, but they were arrayed in such a way that made clamping the Smart Cover to the iPad 2 quite easy."

A small round magnet is located in the Smart Cover just above the array of 12 magnets in its right side. This is the magnet that activates a small inductive sensor embedded in the iPad 2's bezel. This is what powers the Smart Cover's ability to automatically lock the iPad's screen when closed, instead of the NFC technology that was rumored earlier this year.

(Stay tuned for the Ars Technica review of the iPad 2. We plan to post it very soon!)</p)