Zener breakdown in a semiconductor diode occurs when

$A$ Zener diode is used as:

The figure shows a $DC$ voltage regulator circuit with a Zener diode of breakdown voltage $= 6\,V$. If the unregulated input voltage varies between $10\,V$ to $16\,V$, then what is the maximum Zener current in $mA$ (in $.5$)?

$A$ Zener diode acts as a/an

In the given circuit, the breakdown voltage of the Zener diode is $3.0 \, V$. What is the value of $I_z$ (in $ \, mA$)?

$A$ Zener diode with voltage $V_z = 6 \ V$ is used to maintain a constant voltage across a load resistance $R_L = 1000 \ \Omega$. $A$ series resistor $R_s = 100 \ \Omega$ is used. If the source $e.m.f$ is $E = 9 \ V$,then the power dissipated in the Zener diode is .......... $W$.