A long straight wire of radius ' a ' caries a steady current i . The current is uniformly distributed across its cross section. The ratio of the magnetic field at 2 a and 2 a is

Question

A long straight wire of radius ' a ' caries a steady current i . The current is uniformly distributed across its cross section. The ratio of the magnetic field at 2 a ​ and 2 a is

TestHub · Accepted Answer

B 2 π 2 a ​ = μ 0 ​ π a 2 i ​ ( 4 π a 2 ​ ) B 1 ​ = 4 π a μ 0 ​ i ​ … (i) B 2 ​ 2 π ( 2 a ) = μ 0 ​ i B 2 ​ = 4 π a μ 0 ​ i ​ … ( ii ) B 2 ​ B 1 ​ ​ = 1

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