Ohm's law fails in

In order to forward bias a $PN$ junction,the negative terminal of the battery is connected to

In the following circuit,the reading in the ammeter is (in $mA$)

Consider a $p-n$ junction as a capacitor, formed with $p$ and $n$-materials acting as thin metal electrodes and depletion layer width acting as separation between them. Basing on this, assume that an $n-p-n$ transistor is working as an amplifier in $CE$ configuration. If $C_1$ and $C_2$ are the base-emitter and collector-emitter junction capacitances, then :

$A$ $P-N$ junction is formed using $Si$ material. What is the approximate height of the depletion barrier in $V$?

Which of the following diodes is reverse biased?