Question 29 of 276
A long straight wire of a circular cross-section with radius ' ' carries a steady current . The current I is uniformly distributed across this cross-section. The plot of magnitude of magnetic field B with distance from the centre of the wire is given by
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Answer: (D) 
We know inside the wire
$\begin{array}{ll}
B=\frac{\mu_0 I}{2 \pi R^2} \cdot r & (O \lt r \lt R) \\
\text { And } B=\frac{\mu_0 I}{2 \pi r} & \text { for }(R \lt r)
\end{array}$
$\begin{array}{ll}
B=\frac{\mu_0 I}{2 \pi R^2} \cdot r & (O \lt r \lt R) \\
\text { And } B=\frac{\mu_0 I}{2 \pi r} & \text { for }(R \lt r)
\end{array}$
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