In the expression
if we have x >> a2 than the field due to a circular coil, at a far off point on its axis, becomes equal to
We will discuss later that a current carrying circular loop is equivalent to a magnetic dipole with dipole magnetic moment |m| equal to (iA) where A is the area a of the loop and i the current flowing in the loop.
Hence we can will be
which can be shown to be the field due to a (small) magnetic dipole at a far off point.
Hence a current carrying circular loop behaves like a magnetic dipole with magnetic moment.
|m| = iA
