# what is the magnetic field produced by very very thin conductor at any point of it

Only when current flows through thin conductor of infinite length then magnetic field due to a small current element of length dl, at a distance r on a line inclined with conductor by an angle @ is given by

dB = (mu o / 4 pi) * I dl sin @ / r^2

I is the current through conductor , mu o is the permittivity of free space

The above is called Biot-Savart's law

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