Question

Write using biot-savart's law the expression for the magnetic field b vector due to an element

Answer 1

The biot savarts law in vector form can be written as
dB = K Idl ř/r³

Hope this is ur required answer..

Answer 2

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.