When a current of $4 \,A$ changes to $8 \,A$ in $0.6 \,s$ in a primary coil, it induces an e.m.f. of $50 \,mV$ in the secondary coil. The mutual inductance between the two coils is: (in $\,mH$)

$A$ solenoid of length $60 \ cm$ with $15$ turns per $cm$ and area of cross-section $4 \times 10^{-3} \ m^2$ completely surrounds another co-axial solenoid of the same length and area of cross-section $2 \times 10^{-3} \ m^2$ with $40$ turns per $cm$. The mutual inductance of the system is: (in $mH$)

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 in the figure. The variation of $I(t)$ with time can then be represented by the graph labeled as:

$A$ current $I = 10 \sin(100 \pi t) \text{ A}$ is passed in a coil, which induces a maximum emf of $5 \pi \text{ V}$ in a neighboring coil. The mutual inductance of the two coils is: (in $\text{ mH}$)

Two conducting circular loops $A$ and $B$ are placed in the same plane with their centres coinciding as shown in the figure. If $b >> a$,the mutual inductance between them is:

Consider a conducting wire of length $L$ bent in the form of a circle of radius $R$ and another conductor of length $a$ $(a \ll R)$ is bent in the form of a square. The two loops are then placed in the same plane such that the square loop is exactly at the centre of the circular loop. What will be the mutual inductance between the two loops?