A long straight wire of a circular cross-section with radius 'a' carries a steady currentI. The current is uniformly distriuted across this cross-section. The plot of magnitude of magnetic field B with distance r from the centre of the wire is given by

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Solution

Q.
A long straight wire of a circular cross-section with radius 'a' carries a steady current $I$ . The current $I$ is uniformly distributed across this cross-section. The plot of magnitude of magnetic field B with distance r from the centre of the wire is given by [2025]

1

2

3

4 [Ampere's Law]

Ans.
(1)

We know inside the wire

$B = \frac{μ_{0} I}{2 π a^{2}} \cdot r$ (0 < r < a)

And $B = \frac{μ_{0} I}{2 π r}$ for (r > a)

Option (1) is correct answer.

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