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A long straight wire in the horizontal plane carries a current of 50 A in the north to south direction. Give the magnitude and direction of B at a point 2.5 m east of the wire.

The current flowing across the wire has a magnitude of (I) = 50 A.

The point B is 2.5 metres east of the wire.

As a result, the magnitude of the point’s distance from the wire (r) is 2.5 m.

The magnitude of the magnetic field at that place may be calculated using the following equation:

$|\overline B | = \frac{{{\mu _0}2I}}{{4\pi r}}$

where,

${\mu _0} = $Permeability of free space 

$ = 4\pi  \times {10^{ – 7}}Tm{A^{ – 1}}$

$|\overline B | = \frac{{4\pi  \times {{10}^{ – 7}}}}{{4\pi }} \times \frac{{2 \times 50}}{{2.5}}$

$ = 4 \times {10^6}T$

At a distance of 2.5 m, the point is situated normal to the wire length. The current flow in the wire is vertically downward. As a result, the magnetic field at the given position is vertically upward, according to Maxwell’s right-hand thumb rule.