Two tiny wire loops, with areas a1 and a2, are situated a displacement apart (Fig. 7.42)...

Two tiny wire loops, with areas a₁ and a₂, are situated a displacement apart (Fig. 7.42).

(a) Find their mutual inductance. [Hint: Treat them as magnetic dipoles, and use Eq. 5.88.] Is your formula consistent with Eq. 7.24?

(b) Suppose a current I₁ is flowing in loop 1, and we propose to turn on a current I₂ in loop 2. How much work must be done, against the mutually induced emf, to keep the current I1 flowing in loop 1? In light of this result, comment on Eq. 6.35.

Equation 5.88