The Biot–Savart law

Ø   The Biot–Savart law is used for computing the megneic field generated by an elecric current.It relates the magnetic field to the magnitude, direction, length, and proximity of the electric current.The law is valid in the magnetostatic approximation.

                           Electric currents (along closed curve)

Ø   The Biot–Savart law is used for computing the resultant magnetic field B at position r generated by a steady current I, a continual flow of charges which is constant in time and the charge neither accumulates nor depletes at any point.

                                           
Ø   Where

dl is a vector whose magnitude is the length of the differential element of the wire,

μ0 is the magnetic constant,

 is the unit vector of r

Ørsted`s observation

Ø   Ørsted noticed a compass needle deflected from magnetic north when an electric current from a battery was switched on and off, confirming a direct relationship between electricity and magnetism On 21 April 1820.

Ø   According to its his initial interpretation the magnetic effect create from all the side the electric wire.

Ø     After three years he published his finding which is show that an electric current produces a circular magnetic field as it flows through a wire.