$A$ steady current flows in a long wire. It is bent into a circular loop of one turn and the magnetic field at the centre of the coil is $B$. If the same wire is bent into a circular loop of $n$ turns,the magnetic field at the centre of the coil is

The line passing through $\left(-1, \frac{\pi}{2}\right)$ and perpendicular to $\sqrt{3} \sin \theta + 2 \cos \theta = \frac{4}{r}$ is :

Observe the following statements:
$1.$ Heavy water is harmful for the growth of animals.
$2.$ Heavy water reacts with $Al_4C_3$ and forms deuterated acetylene.
$3.$ $BaCl_2 \cdot 2D_2O$ is an example of interstitial deuterate.
The correct statements are:

From the figure describing the photoelectric effect,we may infer correctly that:

In the $HCl$ molecule,the separation between the nuclei of the two atoms is about $1.27 \ \mathring{A}$. The approximate location of the centre of mass of the molecule from the hydrogen atom is ....... $\ \mathring{A}$. (Assuming the chlorine atom to be about $35.5$ times as massive as the hydrogen atom.)

Identify $X$ in the following sequence of reaction:
$C_6H_5-Cl$ $\xrightarrow[CuCN]{KCN} P$ $\xrightarrow{LiAlH_4} Q$ $\xrightarrow{HNO_2} X$