Question

Iron rod Metal ring- Wire coil

1. A conducting ring is falling toward a bar magnet as shown in the figure above. Explain why there will be a repulsive force between the ring and a magnet.

2. A respiration detector can prevent infant sudden death syndrome by sounding an alarm when the infant stops breathing. The detector consists a coil placed on the person’s chest and another on the person’s back. There is a constant current in one coil, but not in the other. Explain how the monitor detects this cessation of breathing.

Answer 1

1.

As the conducting rings falls towards a bar magnet, the magnetic flux through the conducting ring increase. The conducting ring oppose any change in its magnetic flux and hence induce a current in it as per lenz's law. The current is induced in the ring such that it produce its own magnetic field in the direction opposite to the magnetic field by the bar magnet. due to the induced current in the ring, the ring experience magnetic force in upward direction.