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The magnetic field at a distance r from a long wire carrying current i is 0.4 tesla. The magnetic field at a distance 2r is

Answer:

Explanation:

Magnetic field due to long wire,

$B = \frac{\mu_{0}i}{2\pi r}$ or $B\propto\frac{1}{r}$

When r is doubled, the magnetic field becomes half, i.e., now the magnetic field will be 0.2T.