The device used for voltage regulation is

The $I-V$ characteristics of an electronic device are shown in the figure. The device is:

The Zener diode is used for

In a Zener diode,the reverse bias voltage is $3 \ V$ and the width of the depletion region is $300 \ \mathring{A}$. The electric field intensity will be $\dots \ V/cm$.

$A$ certain $p-n$ junction,having a depletion region of width $20 \,\mu m$,was found to have a breakdown voltage of $100 \,V$. If the width of the depletion region is reduced to $1 \,\mu m$ during its production,then it can be used as a zener diode for voltage regulation of .......... $V$.

$A$ Zener diode is to be used as a voltage regulator. Identify the correct setup.