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Let B 1 be the magnitude of magnetic field at centre of a circular coil or radius R carrying current I. Let B 2 be the magnitude of magnetic field at an axial distance ‘x’ from the center. For 4 3 R x = , 1 2 B B is :

1. 16 : 25
2. 25 : 16
3. 64 : 125
4. 4 : 5

Correct answer: 64 : 125

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