Magnetic treasure hunt
Magnetic treasure hunt: detect hidden objects with a magnetometer
Autor:
Titre 4
Learning objectives :
This activity allows students to understand how metal detectors work and explore the magnetic properties of different materials.
Concepts covered
Magnetic field; Magnetic properties of metals; Magnetic detection; Disturbances in the Earth's magnetic field; Ferromagnetism and diamagnetism
What students will do :
The student uses the magnetometer on his smartphone to detect metallic objects hidden under a blanket or in sand. He methodically explores the area by observing variations in the magnetic field and analyzes how these variations differ depending on the size and type of metal of the hidden object.
What is required :
Smartphone with the FizziQ application; Various metal objects of different sizes and compositions; A cover or sandbox to hide objects; FizziQ experience notebook
Scientific background :
A smartphone's magnetometer measures the magnetic field in three spatial directions with a sensitivity of approximately 0.1 μT. Ferromagnetic materials (containing iron, nickel or cobalt) significantly disrupt the Earth's magnetic field (by approximately 25-65 μT) by creating their own local magnetic fields. This property allows their detection even under a layer of sand or earth. The disturbance depends on the mass of the metal, its composition and its distance from the sensor. Objects made of non-ferrous metals (aluminum, copper) are less detectable because they are not magnetizable. This technique is used professionally for the detection of underwater wrecks, landmines or archaeological objects. The main limitation is the detection depth which decreases with object size in an approximate relationship of 10 times the object diameter. The magnetometer on smartphones is sometimes automatically calibrated by the operating system, which can make measurements difficult when moving the device slowly. To get around this problem, FizziQ offers direct access to raw sensor data.