A cardboard tube is wrapped with two windings of insulated wire wound in opposite directions, as in the figure above. Terminals a and b of winding A are connected to a resistor R through a reversing switch, and solenoid winding B is connected to a battery as indicated in the figure. The battery polarity is given in the figure (don't ask your professor). State whether the induced current in the resistor R is from left to right (a to b) or from right to left (b to a) in the following circumstance.
Direction of current in branch a-b at the EXACT moment switch is closed.
b to a
no current is induced since is a DC battery
none of the options
a to b