Question 4: In the above diagrams, a strong bar magnet is moving towards solenoid-2 from solenoid-1. The direction of induced current in solenoid-1 and that in solenoid-2, respectively, are through the directions :
(1) AB and DC
(2) BA and CD
(3) A B and C D
(4) BA and DC
Answer: Option (1)
Explanation:
According to Lenz’s law, the direction of induced current in a coil is such that it opposes the change in magnetic flux producing it.
The bar magnet is moving away from solenoid-1.
Hence, the magnetic flux linked with solenoid-1 decreases.
To oppose this decrease in flux, solenoid-1 must produce a magnetic field that attracts the receding south pole of the magnet.
For this, the face of solenoid-1 near the magnet must behave as a north pole.
Using the right-hand thumb rule, the induced current in solenoid-1 flows from A to B.
The bar magnet is moving towards solenoid-2.
Hence, the magnetic flux linked with solenoid-2 increases.
To oppose this increase in flux, solenoid-2 must produce a magnetic field that repels the approaching south pole of the magnet.
For this, the face of solenoid-2 near the magnet must behave as a south pole.
Using the right-hand thumb rule, the induced current in solenoid-2 flows from D to C.
Therefore, the directions of induced current are AB in solenoid-1 and DC in solenoid-2.