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

The coefficient of mutual induction is $2 \text{ H}$ and the induced e.m.f. across the secondary is $2 \text{ kV}$. The current in the primary is reduced from $6 \text{ A}$ to $3 \text{ A}$. The time required for the change of current is:

The induction coil works on the principle of

The mutual inductance between a primary and secondary circuit is $0.5 \, H$. The resistances of the primary and the secondary circuits are $20 \, \Omega$ and $5 \, \Omega$ respectively. To generate a current of $0.4 \, A$ in the secondary,the current in the primary must be changed at the rate of . . . . . . $A/s$.

Mutual inductance of two coils can be increased by

Find the mutual inductance in the arrangement,when a small circular loop of wire of radius $R$ is placed inside a large square loop of wire of side $L$ $(L \gg R)$. The loops are coplanar and their centres coincide: