Two coils of self-inductance $25 \ mH$ and $9 \ mH$ are placed close together such that the effective flux in one coil is completely linked with the other. The mutual inductance between these coils is (in $mH$)

Two coils of self-inductance $2 \, mH$ and $8 \, mH$ are 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$

What is the coefficient of mutual inductance when the magnetic flux changes by $2 \times 10^{-2} \, Wb$ and the change in current is $0.01 \, A$?

An alternating current of peak value $\left(\frac{2}{\pi}\right) \text{ A}$ flows through the primary coil of a transformer. The coefficient of mutual inductance between the primary and secondary coils is $1 \text{ H}$. What is the peak electromotive force (e.m.f.) induced in the secondary coil (in $\text{ V}$)? (Frequency of a.c. $= 50 \text{ Hz}$)

$A$ circular loop of radius $0.3 \ cm$ lies parallel to a much bigger circular loop of radius $20 \ cm$. The centre of the smaller loop is on the axis of the bigger loop. The distance between their centres is $15 \ cm$. If a current of $2.0 \ A$ flows through the smaller loop,then the flux linked with the bigger loop is $............. \times 10^{-11} \ Wb$.

When magnetic flux changes from $6.5 \times 10^{-2} \ Wb$ to $11 \times 10^{-2} \ Wb$ and the change in current is $0.03 \ A$,the coefficient of mutual inductance will be: (in $H$)