$NPN$ transistors are preferred to $PNP$ transistors because they have

Two rigid bodies $A$ and $B$ rotate with rotational kinetic energies $E_A$ and $E_B$ respectively. The moments of inertia of $A$ and $B$ about the axis of rotation are $I_A$ and $I_B$ respectively. If $I_A = \frac{I_B}{4}$ and $E_A = 100E_B$,then the ratio of the angular momentum of $A$ $(L_A)$ to the angular momentum of $B$ $(L_B)$ is:

Which one of the following is used as an acid flux in metallurgy?

The expression $1+x \log _e a+\frac{x^2}{2 !}(\log _e a)^2+\frac{x^3}{3 !}(\log _e a)^3+\ldots$ for $a>0, x \in R$ is equal to:

$A$ transistor having a $\beta$ equal to $80$ has a change in base current of $250 \mu A$. The change in collector current is:

$A$ and $B$ are two concentric circular loops carrying currents $i_1$ and $i_2$ as shown in the figure. If the ratio of their radii is $1:2$ and the ratio of the magnetic flux densities at the centre $O$ due to $A$ and $B$ is $1:3$,then the value of $\frac{i_1}{i_2}$ will be