5555555555 20. A switch, a 220 Ω resistor, and a 60 mH inductor are in series across a 20 V battery. What is the current through the inductor two time constants after the switch is closed? (a) 91 mA (b) 78 mA (c) 57 mA (d) 400 mA

5555555555 22. Two inductors, L1 and L2, are in parallel. L1 has a value of 25 μH and L2 a value of 50 μH. The parallel combination is in series with L3, a 20 μH coil. The entire combination is across an ac source of 60 Vrms at 300 kHz. The total rms current is ________. (a) 87 mA (b) 870 mA (c) 87 A (d) 337 mA

5555555555 10. The current through a 120 mH coil is changing at a rate of 150 mA/s. The voltage induced across the coil is ________. (a) 1.8 mV (b) 18 mV (c) 180 mV (d) 1.25 mV