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Consider a long straight wire of a circular cross-section (radius a) carrying a steady current I. The current is uniformly distributed across this cross-section. The distances from the centre of the wire's cross-section at which the magnetic field [inside the wire, outside the wire] is half of the maximum possible magnetic field, any where due to the wire, will be :

1. [a/4, 3a/2]
2. [a/2,2a]
3. [a/2,3a]
4. [a/4,2a]

Correct answer: [a/2,2a]

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