Which of the following is the strongest oxidizing agent?

The electric resistance of a certain wire of iron is $R$. If its length and radius are both doubled,then

$A$ hollow metal sphere of radius $5\, cm$ is charged so that the potential on its surface is $10\, V$. The potential at the centre of the sphere is.....$V$

$H_{3}PO_{3}$ can be represented by structures $1$ and $2$ shown below. Can these two structures be taken as the canonical forms of the resonance hybrid representing $H_{3}PO_{3}$? If not,give reasons for the same.

$Assertion\,(A):$ Audio signal of frequency $10 kHz$ cannot be transmitted over long distance without modulation.

$Reason\,(R):$ Length of the antenna required $\lambda /$, should have practical value.

If $y=\tan ^{-1}\left(\frac{\sqrt{1+a^2 x^2}-1}{a x}\right)$,then $\left(1+a^2 x^2\right) y^{\prime \prime}+2 a^2 x y^{\prime}$ is equal to