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A comment on Seagate hits 1 terabit per square inch, 60TB hard drives on their way. Parent comment

Re:Seagate hits 1 terabit per square inch, 60TB hard drives ... by ars on Tuesday March 20, 2012 @04:30PM (#3731360)
Magnetic field strength does not follow any specific dropoff law because it's a dipole.

The dropoff depends on how far apart the ends of the poles are. (i.e. from a distance the two poles blend together and average to zero), it also depends on the orientation - are the poles parallel or perpendicular?

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Re:Seagate hits 1 terabit per square inch, 60TB hard drives ... by mikeash on Tuesday March 20, 2012 @04:35PM (#3731396)
True, but for the common case where the distance from the magnet is substantially greater than the distance between the poles, inverse cube is plenty good enough as an approximation.
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