Biot Savart ’ s Law
The magnetic field produced by a current carrying element of length dl , carrying current I at a point separated by a distance r is given by
dB = μ o / 4 π Idl * r / r 3 or dB = μ o / 4 π Idl sin θ / r 2
where , θ is the angle between the direction of the current and μ o is absolute permeability of the free space .
SI unit of magnetic field is Wm -2 or ( tesla ) and CGS unit of magnetic field is gauss or oersted 1 gauss = 10 -4 tesla .
The direction of magnetic field dB is that of I dl * r .
Magnetic Field Due to a Straight Current Carrying Conductor
where φ1 and φ2 are angles , which the lines joining the two ends of the conductor to the observation point make with the perpendicular from the observation point to the conductor .