A student investigates how the length of a column of dilute saline solution inside a flexible plastic tube affects its electrical resistance.
The student uses a standard ruler to measure the distance between two moveable metal electrodes inserted into the curved tube.
State how the student could improve the precision of the distance measurement.
Suggest three practical steps the student could take to improve the accuracy of this distance measurement.
The student obtains resistance measurements for different lengths of the saline column by passing a current through each length.
Explain why the current in the solution must be kept small.
The table below shows the student's results:
Length of column (cm)Resistance (kΩ)101.4202.8304.2709.88011.29012.6 \begin{array}{|c|c|} \hline \textbf{Length of column (cm)} & \textbf{Resistance (k}\Omega\textbf{)}\\ \hline 10 & 1.4 \\ \hline 20 & 2.8 \\ \hline 30 & 4.2 \\ \hline 70 & 9.8 \\ \hline 80 & 11.2 \\ \hline 90 & 12.6 \\ \hline \end{array} Length of column (cm)102030708090Resistance (kΩ)1.42.84.29.811.212.6Suggest two improvements the student could make to the data collection.
Describe the relationship between the length of the saline column and its resistance shown by these data.
