In a transformer, the coefficient of mutual inductance between the primary and the secondary coil is $0.2 \, H$. When the current changes by $5 \, A/s$ in the primary, the induced $e.m.f.$ in the secondary will be......$V$

$A$ circular loop of radius $0.3 \, cm$ lies parallel to a much bigger circular loop of radius $20 \, cm$. The centre of the small loop is on the axis of the bigger loop. The distance between their centres is $15 \, cm$. If a current of $20 \, A$ flows through the smaller loop,then the flux linked with the bigger loop is:

Two coils are placed close to each other. The mutual inductance of the pair of coils depends upon

The device that does not work on the principle of mutual induction is

If a current of $3.0 \ A$ flowing in the primary coil is reduced to zero in $0.001 \ s$,then the induced $e.m.f.$ in the secondary coil is $15000 \ V$. The mutual inductance between the two coils is (in $H$):

$A$ long straight wire is placed along the axis of a circular ring of radius $R$. The mutual inductance of this system is