Two wires of same length are shaped into a squatr and a circle if they carry same current, ratio of magnetic moment is :
Let the length of each wire be L.
For the square, side = L/4; area = (L/4)² = L²/16.
For the circle, radius = L/2π; area = π(L/2π)² = L² /4π.
Ratio of magnetic moments = L²/4π/L²/16 = 16/4π = 4/π.
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Let the length of each wire be L.
For a square of side a, 4a = L ⟹ a = L/4. Magnetic moment,
M₁ = IA² = I L/4 ².
For a circle of radius r, 2πr = L ⟹ r = L/2π. Magnetic moment,
M₂ =Iπr² = Iπ L/2π ² .
Ration. M₁/M₂ = 2/π.
Answer: (A) 2 : π
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