Two concentric circular loops lie in the same plane. One is connected to a source that supplies an increasing current; the other is a simple closed ring. Is the induced current in the ring in the same direction as the current in the loop connected to the source, or opposite? What if the current in the first loop is decreasing?

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Physics

23 June, 23:45

Two concentric circular loops lie in the same plane. One is connected to a source that supplies an increasing current; the other is a simple closed ring. Is the induced current in the ring in the same direction as the current in the loop connected to the source, or opposite? What if the current in the first loop is decreasing?

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Briggs · Answer 1

We shall apply Lenz's law to solve the problem. This law states that direction of induced current is such that it opposes the change that creates it. Since current increases in the coil it creates increasing magnetic field in the other coil. So the current will be induced in it so that it opposes this increase. It can be done only if current in opposite direction is induced in it. Hence in the first case, current will be induced in opposite direction.

In this case, current is decreasing in the primary coil and current will be induced in the secondary coil. Decreasing current will create decreasing magnetic field. So induced current will try to increase it. In can be done if current in the same direction is induced in the secondary coil.

Hence in the second case, current will be induced in the same direction.