Question
Download Solution PDFThe force between two short bar magnets with magnetic moments M1 and M2 whose centres are r metres apart is 8 N when their axes are in same line. if the separation is increased to 2r, the force between them is reduced to
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFConcept:
The force between two magnetic dipoles varies inversely as the fourth power of the distance between them.
F ∝ 1 / r4
Calculation:
When the separation is r:
F = 8 N
When the separation is increased to 2r:
F' ∝ 1 / (2r)4
⇒ F' ∝ 1 / 16r4
Since initial force F ∝ 1 / r4:
⇒ F' = F / 16
⇒ F' = 8 / 16
⇒ F' = 0.5 N
Hence, the force between the magnets when the separation is increased to 2r is 0.5 N.
∴ The correct answer is option 4.
Last updated on Jul 3, 2025
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