The barrier potential of a $p-n$ junction depends on:
$(1)$ Type of semiconductor material
$(2)$ Amount of doping
$(3)$ Temperature
Which one of the following is correct?

If the two ends $P$ and $N$ of a $P-N$ junction diode are joined by a wire,what happens?

Which of the diode circuits shows the correct biasing used for the measurement of the dynamic resistance of a $p$-$n$ junction diode?

In a $p-n$ junction diode, the thickness of the depletion layer is $2 \times 10^{-6} \,m$ and the barrier potential is $0.3 \,V$. The intensity of the electric field at the junction is

$A$ $p-n$ junction diode can withstand up to $20 \, mA$ current under forward bias. The diode has a potential difference of $0.5 \, V$ across it, which is assumed to be independent of current. What is the maximum voltage of the battery used to forward bias the diode when a resistance of $125 \, \Omega$ is connected in series with it (in $V$)?

$A$ $2\,V$ battery is connected across $AB$ as shown in the figure. The value of the current supplied by the battery when in one case the battery's positive terminal is connected to $A$ and in the other case when the positive terminal of the battery is connected to $B$ will respectively be: