A long straight wire of radius a carries a steady current I. The curre – McqOptions

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1.	A long straight wire of radius a carries a steady current I. The current is uniformly distributed over its cross-section. The ratio of the magnetic fields B and B', at radial distances \[\frac{a}{2}\] and 2a respectively, from the axis of the wire is:
A.	\[\frac{1}{4}\]
B.	\[\frac{1}{2}\]
C.	1
D.	4
Answer» D. 4

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