A current of 1A is flowing on the sides of an equilateral triangle of side 4.5 × 10⁻² m. The magnetic field at the center of the triangle will be -

4 × 10⁻⁵ Wb/m²
Zero
2 × 10⁻⁵ Wb/m²
8 × 10⁻⁵ Wb/m²

Correct answer: 4 × 10⁻⁵ Wb/m²

Solution

For an equilateral triangle, perpendicular distance from centre to a side d = a/(2*sqrt(3)). Field from one side = (mu0*I/4pi/d)*2*sin60. With a=4.5e-2 m, I=1 A, each side gives ~1.33e-5 T; three sides total ~4e-5 Wb/m^2.

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