Magnetic Field Experiments Using a Phone

TL;DR

This paper presents two physics experiments utilizing smartphones to measure magnetic fields, demonstrating their use as accessible sensors for educational purposes in both remote and in-person settings.

Contribution

It introduces novel, practical experiments for measuring magnetic fields with smartphones, including methods for analyzing Earth's magnetic field and earbud magnet fields.

Findings

Smartphones can accurately measure local magnetic fields.

The experiments enable students to determine magnet sizes and positions.

The methods integrate sensor data with curve-fitting techniques.

Abstract

To make physics experiments more directly relevant to everyday life and help students realize how their smart phones or tablets can be used as sensors for scientific measurements, we designed two introductory physics experiments to measure vector magnetic fields. These experiments were initially developed for students working remotely in an online course setting. However, the experiments can also be used for in-person laboratory activities. The first activity uses the phone's three-dimensional sensors to determine the vector components and orientation of the background magnetic field at the students' locations. The resulting vector magnetic field is compared to the expected Earth's magnetic field for their location. The second experiment uses the phone sensors to measure the magnet field produced by the small magnet found in the speaker of common earbuds, or in-ear headphones. The students then carefully investigate the dependence of the magnitude of the field on the axial distance between the speaker magnet and the phone's sensors. Using a ring magnet approximation, advanced Excel curve-fitting methods are introduced to determine the radius of the magnet in the earbud and the distance between the magnet's location and the external surface of the earbud housing.