Carborundum is

The major product of the following reaction is

There are $n$ distinct points on the circumference of a circle. The number of pentagons that can be formed with these points as vertices is equal to the number of possible triangles. Then the value of $n$ is

If $\left[\begin{array}{rrr}1 & -1 & x \\ 1 & x & 1 \\ x & -1 & 1\end{array}\right]$ has no inverse,then the real value of $x$ is

The ratio of specific heats of a gas is $\gamma$. The change in internal energy of one mole of the gas,when the volume changes from $V$ to $2 V$ at constant pressure $p$ is

$A$ long solenoid has $200$ turns per cm and carries a current $i$. The magnetic field at its centre is $6.28 \times 10^{-2} ~Wb/m^2$. Another long solenoid has $100$ turns per cm and it carries a current $\frac{i}{3}$. The value of the magnetic field at its centre is nearly: