Question

The wire ABC shown in figure forms an equilateral triangle. Find the magnetic field B at the centre O of the triangle assuming the wire to be uniform.
Figure

Answer 1

Explanation:

Let current 2I input into the circuit.  

Since the wire is similar, the current at point A (as shown in figure) will be divided equally.  

Magnetic field in P attributable to AB = B wire

(Externally perpendicular to the plane)  

Magnetic field at P due to wire BD = B '

(External perpendicular to the plane)

Magnetic field in P for wire AC = Magnetic field in P for wire AB = B

(Inward-direction  perpendicular to the plane)

Magnetic field in P for wire CD = Magnetic field in P for wire BD = B '

(Inward-direction  perpendicular to the plane)

∴ Total magnetic field at P = B + B’ - B - B’ = 0

The magnetic field B at the centre O of the triangle assuming the wire to be uniform is 0

Answer 2

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Above answer is correct