Which of the following alkali metals reacts directly with nitrogen to form a nitride?

All the diodes are ideal. The current flowing in the $2 \, \Omega$ resistor connected between the diodes $D_1$ and $D_2$ is .......... $A$

The shadow of a tower standing on a level ground is found to be $60 \, m$ longer when the sun's altitude is $30^\circ$ than when it is $45^\circ$. The height of the tower is

The value of $\lambda$ such that $\lambda x^2-10 x y+12 y^2+5 x-16 y-3=0$ represents a pair of straight lines is:

The degree of ionization of $0.10 \ M$ lactic acid is $4.0 \ \%$. The value of $K_a$ is

$A$ transistor is used as an amplifier in $CB$ mode with a load resistance of $5 \, k\Omega$. The current gain of the amplifier is $0.98$ and the input resistance is $70 \, \Omega$. The voltage gain and power gain respectively are: