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.