Force between two identical bar magnets whose centres are r metre apart is 4.8, N , when their axes

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5.Magnetism and Matter

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Force between two identical bar magnets whose centres are $r $ metre apart is $ 4.8\, N$ , when their axes are in the same line. If separation is increased to $2r,$ the force between them is reduced to.....$N$

A

$2.4$

B

$1.2$

C

$0.6$

D

$0.3$

(AIIMS-1995)

Solution

(d)In magnetic dipole, force $ \propto \frac{1}{{{r^4}}}$
Hence new force $ = \frac{{4.8}}{{{2^4}}} = \frac{{4.8}}{{16}} = 0.3\;N$

Standard 12

Physics

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