Write formula for mutual inductance for two very long coaxial solenoids of length $\mathrm{l}$.

Two circuits have mutual inductance of $0.1\, H$. What average $e.m.f$. is induced in one circuit when the current in the other circuit changes from $0$ to $20\, A$ in $0.02$ $s$......$V$

Two circular coils can be arranged in any of the three situations shown in the figure. Their mutual inductance will be

There are two long co -axial solenoids of same length $l.$ The inner and outer coils have radii $r_1$ and $r_2$ and number of turns per unit length $n_1$ and $n_2$ respectively. The ratio of mutual inductance to the self -inductance of the inner -coil is

The mutual inductance between two coils is $1.25$ $henry$. If the current in the primary changes at the rate of $80$ $ampere/second,$ then the induced $e.m.f$ in the secondary is......$V$

A small square loop of wire of side $l$ is placed inside a large square loop of wire of side $(L > l)$. The loop are coplanar and their centre coincide. The mutual inductance of the system is proportional to