First slide
Inductance
Question

A and B are two metallic rings placed at opposite sides of an infinitely long straight conducting wire as shown in figure. If current in the wire is slowly decreased, the direction of the induced current will be

Moderate
Solution

For ring A  : the magnetic field goes outside the plane of the paper. As current in wire decreases, the value of magnetic field also decreases. As per Lenz's law, to oppose this change, current is induced in anticlockwise direction so as to increase the falling value of magnetic field.

For ring B  : the magnetic field goes inside the plane of the paper. As current in wire decreases, the value of magnetic field also decreases. As per Lenz's law, to oppose this change, current is induced in clockwise direction so as to increase the falling value of magnetic field.

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