The barrier potential of a silicon diode is $0.7 \mathrm{V}$ at $25°\mathrm{C}$. Find the barrier potential at $-20°\mathrm{C}$ and at $110°\mathrm{C}$.

Two identical $P$ - $N$ junction may be connected in series with a battery in three ways (figure). The potential drops across the two $P$ -$N$ junction are equal in- 

Figure shows two $p$-$n$ junction diodes along with a resistance $R$ and a DC battery $E$. The path of flow of appreciable current in the circuit is

A semiconductor $X$ is made by doping a germanium crystal with arsenic $\left(Z=33\right)$. A second semiconductor $Y$ is made by doping germanium with indium $\left(Z=49\right)$. The two are joined end to end and connected to a battery as shown in the figure. Which of the following statements is correct?

The diode in the circuit as shown in the figure has constant voltage drop of  $0.5 \mathrm{V}$ at all currents and maximum power rating of $100 \mathrm{mW}$ (milliwatt). What should be the value of resistance $R$, connected in series with the diode for obtaining maximum current?