Two circular loops are placed coaxially but separated by a distance. A battery is suddenly connected to one of the loops establishing a current in it. Will there be a current induced in the other loop? If yes, when does the current start and when does it end? Do the loops attract each other or do they repel?


Let us consider the loops as A and B. When the battery is connected to loop A; the current will flow in a clockwise direction. So the direction of the magnetic field due to the current will be towards left as seen from the loop B. Due to a sudden change in flux through loop A, a current will induce in loop B. But it will only be induced for a moment when the current suddenly jumps from zero to a constant value. After it attained a constant value, there will be no induced current in loop B.


According to the Lenz's law, the direction of the induced current is such that it opposes the magnetic field that has induced it. So the induced current in loop B will be in the opposite direction to the magnetic field of loop A. So the direction of induced current in loop B will be in anticlockwise direction. And the current through loop B will end when the current through loop A becomes zero. Because the directions of the currents in the loops are opposite, they will repel each other.


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