What happens during the regulation action of a Zener diode?

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.......$V$.

Zener breakdown in a semiconductor diode occurs when

Which of the following semi-conducting devices is used as a voltage regulator?

For the circuit shown below,the current through the Zener diode is......$mA$

$A$ Zener diode of breakdown voltage $V_{Z} = 8\,V$ and maximum Zener current $I_{ZM} = 10\,mA$ is subjected to an input voltage $V_{i} = 10\,V$ with a series resistance $R = 100\,\Omega$. In the given circuit,$R_{L}$ represents the variable load resistance. The ratio of the maximum and minimum value of $R_{L}$ is