Two coils $X$ and $Y$ are placed in a circuit such that when a current changes $2A$ in coil $X,$ the magnetic flux changes by $0.4\,weber$ in $Y$. The value of mutual inductance of the coils....$H$

$AB$ is an infinitely long wire placed in the plane of rectangular coil of dimensions as shown in the figure. Calculate the mutual inductance of wire $AB$ and coil $PQRS$

The number of turns of primary and secondary coils of a transformer are $5$ and $10$ respectively and the mutual inductance of the transformer is $25\,henry$. Now the number of turns in the primary and secondary of the transformer are made $10$ and $5$  respectively. The mutual inductance of the transformer in henry will be

Two circular coils have their centres at the same point. The mutual inductance between them will be maximum when their axes

Two coils, $X$ and $Y$, are kept in close vicinity of each other. When a varying current, $I(t)$, flows through coil $X$, the induced emf $(V(t))$ in coil $Y$, varies in the manner shown here. The variation of $I(t)$; with time, can then be represented by the graph labelled as graph

Two coils are placed close to each other. The mutual inductance of the pair of coils depends upon