In the figure,a bar magnet moves away from the solenoid.The direction of the induced current through the resistor R is

Question

Quizplus · Accepted Answer

As the bar magnet moves away from the solenoid, the magnetic field lines around the solenoid start collapsing. According to Faraday's law of electromagnetic induction, a change in magnetic field induces an electromotive force (EMF) which drives a current in a closed circuit. 
In this case, the collapsing magnetic field induces a current in the solenoid in such a direction that it opposes the change in magnetic field. By Lenz's law, the induced current will flow in a direction that creates a magnetic field opposing the motion of the bar magnet. 
The induced magnetic field will be in the opposite direction of the initial magnetic field and towards the left in the figure. 
Therefore, the induced current through the resistor R will be from point a to b, as shown by the arrow in the diagram.

In the Figure,a Bar Magnet Moves Away from the Solenoid