Physics - Current Electricity Question with Solution | TestHub

(1) With $R$ increase, the current $I$ will decrease, so potential gradient will increase. So larger length will be required for a null point. (2) When $S$ is decreased the current drawn from $E_1$ increases. So $\mathrm{V}={\mathrm{E}}_1-\mathrm{Ir}$, the potential difference across ${\mathrm{E}}_1$ will decrease. This new potential difference will be balanced by a smaller length of potentiometer wire.