Two identical coils of inductance $L$ joined in series are placed very close to each other such that the winding direction of one coil is exactly opposite to that of the other. The net inductance is

The energy needed for breaking a liquid drop of radius ' $R$ ' into 216 droplets, each of radius ' $r$ ' is ' $x$ ' times $T R^2$. The value of ' $x$ ' is [ $T=$ surface tension of the liquid].

Out of the following molecules the one which represents the polar molecule is

Six molecules of a gas in container have speeds $2 \mathrm{~m} / \mathrm{s}, 5 \mathrm{~m} / \mathrm{s}, 3 \mathrm{~m} / \mathrm{s}, 6 \mathrm{~m} / \mathrm{s}, 3 \mathrm{~m} / \mathrm{s}$, and $5 \mathrm{~m} / \mathrm{s}$. The r.m.s. speed is