1. The problem statement, all variables and given/known data An inductor is connected to the terminals of a battery that has an emf of 12.0Vand negligible internal resistance. The current is 4.86mA at 0.940ms after the connection is completed. After a long time the current is 6.45mA. 2. Relevant equations V = IR V(t) = V0 (exp(-t/τ)) 3. The attempt at a solution At infinite time, an inductor appears like a wire. Therefore, 12V = 6.45mA * R R = 1860 Ohms V(t) = V0 exp(-t/(L/R)) (4.86mA * 1860 Ohm) = 12V exp(-t/(L/R)) .753 = exp(-t/(L/R)) natural log both sides... .28 = t / (L/R) L/R = 0.0033 L = 6.18 H However, MasteringPhysics does not accept this solution.