Textbook formula for field intensity in solenoid coil is
H = (N * I) / l
H magnetic field intensity in ampere-turns
l is length between the coil poles (along the axis of the field flux)
This formula does not take into consideration the width (or diameter) of the coil. Apparently it is based on assumption that diameter is smaller than the length and hence does not significantly impact this calculation.
I am considering a single electromagnet as a model for a BLDC motor' stator coil. Those are often more wider coil diameter and of short coil length. Wider coil surely weakens the intensity of the field inside the coil. Imagine the flux lines getting thinner as the coil loops get wider. How to reflect this fact in the calculation of the field? How to adjust that formula to include the width/diameter of the coil?
Also, a bit aside from the main question, please give me a hint How to calculate the attracting force developed in such a wide solenoid in Newtons, knowing field intensity and, say, attracting an iron cylinder of known mass and permeability ? Note: for the sake of simplicity assume air core in solenoid.
Edit: if my second question seems to spill into larger area of expertise please disregard it and simply suggest the answer to the main question as it is important for finding if the range of the field stays below the saturation point.