Two concentric circular coils,one of small radius $r$ and the other of large radius $R$,are placed coaxially with their centers coinciding. If the radius $r$ is changed by $2 \%$,then the change in mutual inductance of the arrangement is (assume $r \ll R$). (in $\%$)

$A$ small square loop of wire of side $l$ is placed inside a large square loop of wire $L$ $(L \gg l)$. Both loops are coplanar and their centres coincide at point $O$ as shown in the figure. The mutual inductance of the system is:

Two concentric coplanar circular conducting loops have radii $R$ and $r$ $(R \gg r)$. Their mutual inductance is proportional to

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:

$A$ small circular loop of wire of radius $a$ is located at the centre of a much larger circular wire loop of radius $b$. The two loops are in the same plane. The outer loop of radius $b$ carries an alternating current $I = I_0 \cos (\omega t)$. The emf induced in the smaller inner loop is nearly

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$