Physics - Current Electricity Question with Solution | TestHub

Current through${\mathrm{R}}_4$(as well as${\mathrm{R}}_3$) is${\mathrm{i}}_1=\frac{\mathrm{V}}{\mathrm{R}}=\frac{5}{500}=10\mathrm{ }\mathrm{mA}$

Potential drop across$400 \mathrm{\Omega }$is

${\mathrm{V}}_{400}=18-10\times {10}^{-3}\times 600$

$=12\mathrm{ }\mathrm{V}$

Current through battery,

$\mathrm{I}=\frac{12}{400}=30\mathrm{ }\mathrm{mA}$

$\therefore$Current through${\mathrm{R}}_2$,${\mathrm{i}}_2=30-10$$=20\mathrm{ }\mathrm{mA}$

$\therefore {\mathrm{R}}_2=\frac{6}{20\times {10}^{-3}}=300\mathrm{ }\mathrm{\Omega }$