Which nitrogenous base is present in $RNA$ but not in $DNA$?

Consider the situation shown in the figure. The wire $AB$ is sliding on the fixed rails with a constant velocity $V$. If the wire $AB$ is replaced by a semicircular wire of the same chord length,the magnitude of the induced current will

Energy required to remove an electron from an aluminium surface is $4.2 \text{ eV}$. If light of wavelength $2000 \text{ \AA}$ falls on the surface, the velocity of the fastest electron ejected from the surface will be:

If $f(x)=x e^{x(1-x)}$,then $f(x)$ is

The number of ways that $8$ beads of different colours can be strung as a necklace is

In the circuit shown, if a conducting wire is connected between points $A$ and $B$, the current in this wire will