$A$ Zener diode,having a breakdown voltage equal to $15\ V$,is used in a voltage regulator circuit as shown in the figure. The current through the Zener diode is $.....\ mA$.

Two cylinders $A$ and $B$ fitted with pistons contain equal amounts of an ideal diatomic gas at $300\,K$. The piston of $A$ is free to move,while that of $B$ is held fixed. The same amount of heat is given to the gas in each cylinder. If the rise in temperature of the gas in $A$ is $30\,K$,then the rise in temperature of the gas in $B$ is .... $K$.

If the water falls from a dam into a turbine wheel $19.6\, m$ below,then the velocity of water at the turbine is ............. $m/s$ $(g = 9.8\,m/s^2)$.

$100$ cells each of e.m.f. $5 \ V$ and internal resistance $1 \ \Omega$ are to be arranged so as to produce maximum current in a $25 \ \Omega$ resistance. Each row is to contain equal number of cells. The number of rows should be

The rods of length $L_1$ and $L_2$ are made of materials whose coefficients of linear expansion are $\alpha_1$ and $\alpha_2$. If the difference between the two lengths is independent of temperature,then:

$A$ thermodynamic system undergoes a cyclic process $ABCDA$ as shown in the figure. The work done by the system in the cycle is