14) shows a plot of the magnitude of B with distance r
from the centre of the wire The direction of the field is tangential to
the respective circular loop (1 or 2) and given by the right-hand
rule described earlier in this section This example possesses the required symmetry so that Ampere’s
law can be applied readily It should be noted that while Ampere’s circuital law holds for any
loop, it may not always facilitate an evaluation of the magnetic field in
every case