$A$ pair of adjacent coils has a mutual inductance of $1.5 \ H$. If the current in one coil changes from $0$ to $20 \ A$ in $0.5 \ s$,what is the change of flux linkage with the other coil (in $Wb$)?

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 $H$)

$A$ long solenoid '$S$' has 'n' turns per meter,with diameter 'a'. At the centre of this coil we place a smaller coil of '$N$' turns and diameter 'b' (where $b < a$). If the current in the solenoid increases linearly with time,what is the induced emf appearing in the smaller coil? Plot a graph showing the nature of variation in emf,if current varies as a function of $I(t) = mt^2 + C$.

$A$ short solenoid (length $l$ and radius $r$ with $n$ turns per unit length) lies well inside and on the axis of a very long,coaxial solenoid (length $L$,radius $R$ and $N$ turns per unit length,with $R > r$). Current $I$ flows in the short solenoid. Choose the correct statement.

Derive the formula for mutual inductance of two very long coaxial solenoids. Also,discuss the reciprocity theorem.

$A$ primary coil and a secondary coil are placed close to each other. $A$ current, which changes at the rate of $25 \, A$ in a millisecond, is present in the primary coil. If the mutual inductance is $92 \times 10^{-6} \, H$, then the value of the induced emf in the secondary coil is: