Two circular, concentric and coplanar turns of
radii R1 = 30 cm and R2 = 20 cm are traversed by currents
i1 = 5 A and i2 = 2 A, indicated in the figure. being the constant of
magnetic permeability in vacuum μ0 = 4^.10-7 Tm/A,
characterize the magnetic induction vector originating at center O.