Page 483 - Basic Electrical Engineering

and

Figure 5.9

The resultant of the two vectors PQ and PR were give the net magnetizing

field intensity

To determine the total H, we have to integrate the above expression as

If the circular coil has N number of turns, then

For determining the field strength at the centre of the current-carrying coil,
we put d = 0. Thus, the magnetic field strength, the H at the centre of the coil
c
is