Two coils of self inductances $2\, mH$ and $8\, mH$ Hare placed so close together that the effective flux in one coil is completely linked with the other. The mutual inductance between these coils is......$mH$

A small square loop of wire of side $\ell$ is placed inside a large square loop of wire of side $L$ $\left(\mathrm{L}=\ell^2\right)$. The loops are coplanar and therr centers coinside. The value of the mutual inductance of the system is $\sqrt{\mathrm{x}} \times 10^{-7} \mathrm{H}$, where X =___

In a $dc$ motor, induced $e.m.f.$ will be maximum

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....$H$

If a change in current of $0.01\, A$ in one coil produces a change in magnetic flux of $1.2 \times {10^{ - 2}}\,Wb$ in the other coil, then the mutual inductance of the two coils in henries is.....$H$

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