Zener diode acts as a/an

In the given circuit- the value of current $I _{ L }$ will be $mA$.

(When $R _{ L }=1 \,k\, \Omega$ )

Zener breakdown in a semi-conductor diode occurs when

Zener breakdown takes place if

Two Zener diodes ($A$ and $B$) having breakdown voltages of $6\, V$ and $4\, V$ respectively, are connected as shown in athe circuit below. The output voltage $V _{0}$ variation with input voltage linearly increasing with time, is given by : $\left( V _{\text {input }}= OV \right.$ at $\left. t =0\right)$ (figures are qualitative)