An electron moves in a circular orbit with a uniform speed $v$. It produces a magnetic field $B$ at the centre of the circle. The radius of the circle is proportional to

The technique of obtaining a large number of plantlets by tissue culture method is called:

If $I$ is the identity matrix of order $2$ and $A = \begin{bmatrix} 1 & 1 \\ 0 & 1 \end{bmatrix}$,then for $n \geq 1$,mathematical induction gives

Which of the following haloalkanes will undergo $S_{N}2$ reaction at the fastest rate?

In an electrochemicalcell, dichromate ions in aqueous acidic medium are reduced to $Cr ^{3+}$. The current $($in amperes$)$ that flows through the cell for $48.25$ minutes to produce $1$ mole of $Cr ^{3+}$ is $....$ . Use: $1$ Faraday $=96500 C mol ^{-1}$

$A$ circular disc of radius $R$ is removed from a bigger circular disc of radius $2R$ such that the circumferences of the discs touch. The centre of mass of the new disc is at a distance $\alpha R$ from the centre of the bigger disc. The value of $\alpha$ is