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The strength of a bar magnet's magnetic field decreases with distance according to what is known as an inverse cube law; multiplying the distance from the magnet by a factor of k divides the magnetic field strength by a factor of \(k^3\)  .Suppose the magnetic field strength of the magnet is 64 Gauss at a distance of 10cm away. What is the magnetic field strength of the magnet, 20cm away?

 Jul 14, 2017
 #1
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Since the strength of the magnet decreases as the inverse cube of the distance, therefore:

64 x 1/(20/10)^3 =

64 x 1/2^3 =

64 x 1/8 =8 gauss - the strength of the magnet at 20 cm.

 Jul 14, 2017
edited by Guest  Jul 14, 2017
 #2
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At  2 times the distance   it's  1/(2)^3    = 1/8 of the strength   which is   8

 

At 3 times the distance it would be 1/(3^3)

 

and at 4 times the distance it would be 1/(4^3)     and so on.

 Jul 14, 2017

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