Physics - Current Electricity Question with Solution | TestHub

Potential gradient $k=1\text{ mV/cm}=\frac{10^{-3}\text{ V}}{10^{-2}\text{ m}}=0.1\text{ V/m}$

Length of the potentiometer wire $L=4\text{ m}$

Potential difference across the potentiometer wire $V=k\times L=0.1\times 4=0.4\text{ V}$

Current in the circuit $I=\frac{V}{R_p}=\frac{0.4}{8}=0.05\text{ A}$

Total resistance of the circuit $R_{eq}=\frac{E}{I}=\frac{2}{0.05}=40\Omega$

Resistance to be connected in series $R=R_{eq}-R_p=40-8=32\Omega$

Answer: $32\Omega$