A long straight conductor carrying current `I_1` is placed in the plane of a ribbon carrying current `I_2` parallel to the previous one. The width of the ribbon is b and the straight conductor is at a distance a from the near endge. Find the force of attraction between the two.

Explanation

dF (force of attraction) deu to thin strip of thickness dx at a distance x
`dF = (mu_(0) I_(1))/(2 pi x) ((i_(2) dx)/(b))`
`F = (mu_(0) I_(1) i_(2))/(2 pi b) underset(a)overset(a + b)(int) (Dx)/(x) = (mu_(0) I_(1) I_(2))/(2 pi b) In ((a + b)/(b))`