Two students use a digital Gaussmeter with a Hall probe to investigate how the magnetic flux density of a compact electromagnetic coil varies with distance along its central axis. The Gaussmeter only displays integer readings in Gauss (G\text{G}G).
The table below shows their results:
Distance (mm)Magnetic flux density (G)5.018010.08515.04020.02025.01230.0835.0540.0545.05\begin{array}{|c|c|} \hline \textbf{Distance (mm)} & \textbf{Magnetic flux density (G)} \\ \hline 5.0 & 180 \\ 10.0 & 85 \\ 15.0 & 40 \\ 20.0 & 20 \\ 25.0 & 12 \\ 30.0 & 8 \\ 35.0 & 5 \\ 40.0 & 5 \\ 45.0 & 5 \\ \hline \end{array}Distance (mm)5.010.015.020.025.030.035.040.045.0Magnetic flux density (G)180854020128555Each student displays the results as a different graph:
Discuss which graph (Graph P or Graph Q) is best for displaying this type of data.
Suggest how the students could improve the accuracy of their distance measurement.
Suggest why the reading on the Gaussmeter remains constant at 5 G5\text{ G}5 G for the last three readings.
Different alloy foils can be used for magnetic shielding. The students modify their investigation to measure how effective different alloy foils are at shielding magnetic fields. They place a thin foil sheet of a test alloy between the electromagnetic coil and the Hall probe. Describe how the students should control the variables in this new investigation.