The graph given below represents $I-V$ characteristics of a Zener diode. The part of the characteristics curve that is most relevant for its operation as a voltage regulator is

$A$ voltage regulating circuit consisting of a Zener diode, having a breakdown voltage of $10 \ V$ and a maximum power dissipation of $0.4 \ W$, is operated at $15 \ V$. The approximate value of the protective resistance in this circuit is . . . . . . $\Omega$.

If the voltage between the terminals $A$ and $B$ is $17\ V$ and the Zener breakdown voltage is $9\ V$,then the potential voltage across $R$ is.......$V$.

In the following circuit,the power dissipated in the Zener diode is (in $W$)

$A$ Zener diode of power rating $2 \, W$ is to be used as a voltage regulator. If the Zener diode has a breakdown voltage of $10 \, V$ and it has to regulate an unregulated input voltage that fluctuates between $6 \, V$ and $14 \, V$, the value of $R_s$ for safe operation should be $.... \Omega$.

In the following circuit,the current flowing through the $1\,k\Omega$ resistor is......$mA$.