force between two identical bar magnets whose centres are r metre apart is 4.8N. when their axes are in the same line..if separation is increased to 2r,the force between them is reduced to
a) 2.4N
b) 1.2N
c) 0.6N
d) 0.3N

0.6 N
because v know that it varies inversely with cube of r.
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Pls tell me two things -
1 is d ans correct ?
2 Are these previous AIEEE que ?
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No.. AIIMS previous year ques..
but i know that whenever magnetic moment is mentioned and something which seems that the ques relates to magnetic moment then we should use
force is inversely proportional to r3, but here in the solution it is given that force varies inversely to r4..
i think r4 is only written when we write vector relation..

and ans is 0.3
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Sister I think force is inversely proportional to r² then how it comes to r³ n r⁴
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Yes you are right.
In magnetic dipole,
Force in inversely proportional to r?
4.8/F = (2r/r)?
?F = 4.8/16 = 0.3N
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Just consider it analogous two force between two dipoles.... We know that the force in this case is inversely proportional to r4, same pattern can be followed in this case also. Hope it helps.
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Correct answer is 0.3
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Here's the answer

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Force bw 2 dipoles is always inverse to r4
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This is similar formula in electrostatics +q is similar to +m or north pole and -q is similar to -m or north pole

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-m is similar to South pole sorry
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1/4π€ is similar to u/4€
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Dear student,
Their axes are in same line indicates they are two magnetic dipole side by side,

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Coulomb's inverse square law says that the force between two magnetic poles is inversely proportional to the square of the distance between them So F= K× m' × m / ( d^ 2) So 4.8 / F = 4 r^ 2/r^2 So and is 1.2 But they gave the as 0.3 by mistake
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d) 0.3
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What are you looking for?