Using Lenz’s law, determine the direction of the current in resistor ab of Fig. E29.19 w...

Using Lenz’s law, determine the direction of the current in resistor ab of Fig. E29.19 when (a) switch S is opened after having been closed for several minutes; (b) coil B is brought closer to coil A with the switch closed; (c) the resistance of R is decreased while the switch remains closed.