Figure shows a long and thin strip of width b which carries a current `I`. Find magnetic induction due to the current in strip at point P located at a distance `r` from the strip in the plane of strip as shown in figure-4.35.

Explanation

`dB = (mu_(0))/(4pi) (2l')/(x)`
Where `l' = (l)/(b) dx`
`dB = (mu_(0))/(4pi) (2l)/(b) (dx)/(x)`
So, `B = (mu_(0))/(4pi) (2l)/(b) underset(a)overset(a + b)int (dx)/(x) = (mu_(0))/(4pi) (2l)/(b) log_(e) [1 + (b)/(a)]`