The force between two magnet poles separated by a distance 'd' in air is 'F'. At what distance between them does the force become doubled ?

Explanation

Force between two magnetic poles, `F_(1) = F`,
Distance between two magnetic poles, `d_(1) = d`
Force between two magnetic poles increased by double `F_(2) = 2F`
Distance between two magnetic poles, `d_(2) = ?`
From Coulombs law, `F_(1)d_(1)^(2) = F_(2)d_(2)^(2)`
`Fd^(2) = 2F d_(2)^(2)`
`rArr d_(2)^(2) = (d^(2))/(2)`
`:. d_(2) = (d)/(sqrt(2))`