5.16  

Two long coaxial solenoids each carry a current I, but in opposite directions, as shown in Fig 5.42. The inner solenoid (radius a) has n₁ turns per unit length, and the outer one (radius b) has n₂ turns per unit length. Find B in each of the three regions: (i) inside the inner solenoid, (ii) between them, and (iii) outside both.

Figure 5.42