Find the magnetic field at point P on the axis of a tightly wound solenoid (helical coil...

Find the magnetic field at point P on the axis of a tightly wound solenoid (helical coil) consisting of n turns per unit length wrapped around a cylindrical tube of radius a and carrying current I (Fig. 5.25). Express your answer in terms of θ₁ and θ₂ (it’s easiest that way). Consider the turns to be essentially circular, and use the result of Ex. 5.6. What is the field on the axis of an infinite solenoid (infinite in both directions)?

Figure 5.25

Reference example 5.6

Find the magnetic field a distance z above the center of a circular loop of radius R, which carries a steady current I (Fig. 5.21).