(a) State Bio-Savart's law in vector form expressing the magnetic field due to an element `vecdl` carrying current I at a distance r from the element.
(b) Write the expression for the magnitude of the magnetic field at the centre of a circular loop of radius 'R' carrying a steady current I. Draw the field lines due to the current loop.

Explanation

(b) The magnitude of magnetic field is given as `B = (mu_0 I)/(2R)`
Field lines have been drawn in fig.