CBSE Class 12 · 2012 · Electromagnetic InductionVery Short Answer

Predict the directions of the induced currents in metal rings 1 and 2 lying in the same plane, where the current

I

in the straight wire is increasing steadily.

Answer: Ring 1: clockwise; Ring 2: anticlockwise (as seen in the figure).

Solution

The straight wire sets up a magnetic field that is into the plane on one side of the wire and out of the plane on the other.
As

I

increases, the flux through each ring grows in magnitude. By Lenz's law each ring drives a current that opposes this increase.
Ring 1 (above the wire) and Ring 2 (below the wire) sit in oppositely directed fields, so their induced currents circulate in opposite senses: the current in ring 1 is clockwise and in ring 2 is anticlockwise.

CBSE Class 12 Board · 2012 · Subjective

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