A straight wire segment of length 8 meters carries a current of 8 Amps. Find the strength of the magnetic field at a point lying 3.2 meters from the segment, if the segment is perpendicular to a vector from the center of the segment to the point.
The magnetic field at a point P due to a short current segment, with point P lying 'at a perpendicular' to the segment, is proportional to the current and the length of the segment.
The specific value of the magnetic field is given by B=k ' (IL)/r ^ 2.
Thus
Just as the electric field strength E = k q / r^2 of a point charge q falls off as the inverse square of distance from the source q, the magnetic field B = k' (IL) / r^2 of a short charge-and-length segment IL falls of as the inverse square of its distance from the source IL.
The magnetic field is a little trickier than the electric field, since it depends not only on distance but on the orientation of the point with respect to the direction of the current I from which it arises. However
The direction of the magnetic field is found by the right-hand rule: