b
Potential difference $\mathrm{V}_{\mathrm{P}}$ across $\mathrm{P}$ as determined
from $\mathrm{E}_{1}$ is given by $\mathrm{V}_{\mathrm{P}}=\left(\frac{\mathrm{E}_{1}}{\mathrm{P}+\mathrm{Q}}\right) \mathrm{P}.$
Also, $\mathrm{V}_{\mathrm{P}}=\mathrm{E}_{2}$. Therefore,
$\mathrm{E}_{2}=\mathrm{E}_{1}\left(\frac{\mathrm{P}}{\mathrm{P}+\mathrm{Q}}\right) \Rightarrow \frac{\mathrm{E}_{2}}{\mathrm{E}_{1}}=\frac{\mathrm{P}}{\mathrm{P}+\mathrm{Q}}$