Neco 2020 Physics Question 50

In a laboratory the terminal voltage \(V\) of a battery is measured for different currents \(I\) by varying an external resistance. The recorded data are:\n\n\[\n\begin{array}{c|c}\nI\ (\text{A}) & V\ (\text{V}) \\ \hline\n0.10 & 1.45 \\ \n0.20 & 1.38 \\ \n0.30 & 1.31 \\ \n0.40 & 1.24 \\ \n0.50 & 1.17\n\end{array}\n\]\n\nAssuming the relationship \(V = E - Ir\) (where \(E\) is the emf and \(r\) the internal resistance), (a) determine \(E\) and \(r\) using the first and last data points, (b) estimate the standard uncertainty in \(r\) if the voltage measurement uncertainty is \(\pm0.01\,\text{V}\) and the current uncertainty is negligible, and (c) identify one possible source of systematic error in the experiment and suggest a method to reduce it.