In a $p-n$ junction diode,change in temperature due to heating

The $I-V$ characteristics of a $p-n$ junction diode in forward bias is shown in the figure. The ratio of dynamic resistance,corresponding to forward bias voltages of $2 \; V$ and $4 \; V$ respectively,is

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

Different voltages are applied across a $P-N$ junction and the currents are measured for each value. Which of the following graphs is obtained between voltage and current?

Application of a forward bias to a $P-N$ junction

$A$ $2V$ battery is connected across the points $A$ and $B$ as shown in the figure. Assuming that the resistance of each diode is zero in forward bias and infinity in reverse bias,the current supplied by the battery when its positive terminal is connected to $A$ is........$A$