Describe the Bio-Savart law?

Biot Savart  Law states that
The magnetic intensity dH at a point A due to current I flowing through a small element dl is
1)Directly proportional to current (I)
2)Directly proportional to the length of the element (dl)
3)Directly proportional to the sine of angle θ between the direction of current and the line joining the element dl from point A.
4)Inversely proportional to the square of the distance (x) of point A from the element dl.

where k is constant and depends on the magnetic properties of the medium.

µ0 = absolute permeability of air or vacuum and its value is 4 x 10-7 Wb/A-m
µr= relative permeability of the medium.