# 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 and 2a respectively, from the axis of the wire is: Option 1) Option 2) Option 3) 1 Option 4) 4

For Infinite Length -

- wherein

Magnetic field at a point inside the wire at a distance   from the axis of wire is

Magnetic field at a point out side the wire at distance r=2a from the axis of wive is

Option 1)

This is incorrect option

Option 2)

This is incorrect option

Option 3)

1

This is correct option

Option 4)

4

This is incorrect option

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