A student wishes to verify experimentally how the magnitude of the magnetic field…
PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
A student wishes to verify experimentally how the magnitude of the magnetic field produced by a neodymium sphere magnet depends on distance. The student has access to a smartphone magnetometer app that displays the local field magnitude in microteslas.
(a) Design an experimental procedure the student could follow to collect data that reveal the functional dependence of magnetic field strength on distance from the magnet along a chosen axis. Include how distances will be measured and which variables will be controlled.
(b) Describe how the student should analyze the collected data to decide whether the dependence follows an inverse-square, inverse-cube, or some other power-law relationship.
(c) Explain how nearby high-permeability objects (for example, steel table legs) could affect the measurements and propose strategies to minimize these effects.
(d) Suppose the student’s linearized graph of the data yields a slope of −3.1. Interpret this slope in the context of magnetic dipole theory and comment on possible sources of the small discrepancy from the expected theoretical value.