Which of the following elements does not form a monoxide?

$A$ prism of refractive index $\mu$ and angle $A$ is placed in the minimum deviation position. If the angle of minimum deviation is $A$, then the value of $A$ in terms of $\mu$ is :

The ratio of the magnetic field at the centre of a current-carrying circular wire and the magnetic field at the centre of a square coil made from the same length of wire will be

Assertion $(A)$ The effective resistance of the network between $P$ and $Q$ is $\frac{4}{5} r.$

Reason $(R):$ Symmetry can be applied to be network with respect to centre.

The phenomenon of 'industrial melanism' demonstrates:

An inductance of $1 \ H$ is connected in series with an $AC$ source of $220 \ V$ and $50 \ Hz$. The inductive reactance (in ohm) is (in $\pi$)