CBSE Class 12 · 2008 · SemiconductorsShort Answer

(i) The characteristic shows a sharp reverse breakdown at a definite voltage, which identifies a zener diode.
(ii) To obtain it, connect the zener in reverse bias to a variable supply through a series resistance $R_S$, with a voltmeter across the diode and a milliammeter in series.
(iii) Beyond the zener voltage $V_z$ the voltage across the diode remains essentially constant while the current changes greatly.
Connecting the load in parallel with the zener (with $R_S$ in series) keeps the load voltage fixed at $V_z$ despite supply or load changes — voltage regulation.
$\boxed{\text{Zener diode; constant }{V}_z\text{ in breakdown regulates voltage.}}$