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Problem 7 - Olympiad

Two square coils (each of side 0.3 m) are arranged coaxially. The first has 5000 turns and carries a current of 2 A. The second has 30 turns. If the axis is perpendicular to the plane of coils, what is the coefficient of coupling?

Correct: B

Coefficient of coupling (k) < 1. For coaxial perpendicular planes, coupling is minimal. Standard values suggest k ~ 0.1 for such arrangements.