Answer
a A clockwise current is induced in the wire ring.
b. No current is induced in the ring.
c. A counterclockwise current is induced in the wire ring.
Work Step by Step
a. Yes, a current is induced in the wire, due to the changing magnetic flux.
Magnetic field lines point toward the south pole of the magnet. As you push the magnet as described, the number of magnetic field lines coming through the loop, pointing toward you, increases with time.
The induced current in the loop will cause a field to oppose this change in magnetic flux. The secondary field makes magnetic field lines through the loop that point away from you. By the right hand rule, a clockwise induced current appears in the ring.
b. No current is induced in the ring when the magnet is held steady. A stationary magnet means that the magnetic flux through the ring is not changing. No emf appears, and no current is induced.
c. Yes, a current is induced in the wire when you withdraw the magnet, due to the changing magnetic flux.
Magnetic field lines point toward the south pole of the magnet. As you withdraw the magnet as described, the number of magnetic field lines coming through the loop, pointing toward you, decreases with time.
The induced current in the loop will cause a field to oppose this change in magnetic flux. The secondary field makes magnetic field lines through the loop that point toward you, to replace field that is lost. By the right hand rule, a counterclockwise induced current appears in the ring.