The mutual inductance between two planar concentric rings of radii r1 and r2 (with r1>>r2) placed in air is given by
If the sum of the areas of two circles with radii R1 and R2 is equal to the area of a circle of radius R, then
If the sum of the areas of two circles with radii R1 and R2 is equal to the area of a circle of radius R then
(a) R1+R2=R
(b) R1+R2>R
(c) R21+R22<R2
(d) R21+R22=R2