Two solenoids of equal length but different number of turns per unit length are placed coaxially. $n_2$ and $n_1$ are the number of turns per unit length of outer and inner solenoids respectively. Radius of inner and outer solenoids are $R_1$ and $R_2$ respectively. The ratio of mutual inductance to self inductance of inner inductor is

Consider two coils of radii $r_1$ and $r_2$, placed at a distance $d$ away as shown in the figure. Assuming the length of the coils $l_1,l_2\gg d$ with $n_1,n_2$ the number of turns per unit length of the two coils respectively, the mutual inductance of the two coils is

Two inductors $L_1$ and $L_2$ are connected in parallel and a time varying current flows as shown in figure. The ratio ot current $\frac{i_1}{i_2}$ at any ime $t$ Is