Question
(a) Write using Biot - Savart Law, the expression for magnetic field →B due to an element →dl carrying current I at a distance →r from it in a vector form.
Hence derive the expression for the magnetic field due to a current carrying loop of radius R at a point P distant x from its centre along the axis of the loop.
(b) Explain how Biot - Savart law enables one to express the Ampere's circuital law in the integral form, viz.,
→B.→dl=μoI
where I is the total current passing through the surface.