The element used by Rutherford in his famous scattering experiment was

The number of molecules in $16 \ g$ of methane is

The three-domain system of classification is based on which of the following criteria?

If the polar of a point on the circle $x^2+y^2=p^2$ with respect to the circle $x^2+y^2=q^2$ touches the circle $x^2+y^2=r^2$,then $p, q, r$ are in

There are two coils $A$ and $B$ as shown in the figure. No current flows in $B$ if $A$ is at rest. Now,the coil $A$ is made to rotate about a vertical axis. At the shown instant $(t = 0)$,what will be the direction of the current in coil $A$ if the induced current in coil $B$ is counterclockwise?

$A$ wire in the form of a square of side '$a$' carries a current $i$. Then the magnetic induction at the centre of the square wire is (Magnetic permeability of free space = $\mu_0$)