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  • A long straight wire of circular cross-section (radius a) is carrying steady current I. The current I is uniformly distributed across this cross-section. The magnetic field is<div class=

A long straight wire of circular cross-section (radius a) is carrying steady current I. The current I is uniformly
distributed across this cross-section. The magnetic field is

Option: 1

zero in the region r < a and inversely proportional to r in the region r > a
 


Option: 2

 inversely proportional to r in the region r < a and uniform throughout in the region r > a
 


Option: 3

directly proportional to r in the region r < a and inversely proportional to r in the region r > a
 


Option: 4

uniform in the region r < a and inversely proportional to distance r from the axis, in the region r > a


Answers (1)

best_answer

It is a case of solid infinite current-carrying wire. Using ampere circuital law,
\begin{aligned} &CASE I: if \ \ r \leq R \\ &B=\frac{\mu_0 i}{2 \pi R^2} r\\ &CASE II: > R\\ &B=\frac{\mu_0 i}{2 \pi r} \end{aligned}

Posted by

Ajit Kumar Dubey

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