Given: The current carried over power line is , the distance of the point from the line is .
Magnetic field at a point due to power line is given as,
where, the permeability of free space is , current carried by the power line is , and the distance of the point is .
By substituting the given values in the above equation, we get,
Therefore, the magnetic field at a point due to power line is . From right hand thumb's rule, the direction of the magnetic field at the observation point is towards the south.