Figure shows a long wire bent at the middle to form a right angle. Show that the magnitudes of the magnetic field at point P, Q,R and S are equal and find this magnitude.

Explanation

`|B_P|=(mu_0i)/(4pid), |B_R|=(mu_0i)/(4pid)`
At P and R, the field due to vetical part is zero and the points
are equidistant form the horizontal wire. Similarly, the point
S and Q are equidistant from the vertical wire and field due to
horizontal wire is zero.
Hence `|B_Q|=|B_S|=(mu_0i)/(4pid)`
`implies |B_P|=|B_Q|=|B_R|=|B_S|=(mu_0i)/(4pid)`