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The sensor used for detecting magnetism is called a magnetometer. When a magnetic field is present, the electrons flowing in the sensor will be attracted to the north direction of the magnetic field. The electron deflection causes a voltage difference which is called the Hall voltage. The sensor detects the Hall voltage to measure the strength of the magnetic field.

Read more about all the sensors in your phone:

Read more about microelectromechanical sensing systems:

Read more about Hall-effect sensors:

Downloadable  worksheet version of these activities:

Activity 1

Find The Location Of The Magnetometer On Your Phone

Did you know that there is a magnetometer in your phone? A magnetometer measures magnetic fields. Its purpose on your phone includes compass-related functionalities. Let's find out more about the sensors in your phone!

So how do you use the magnetometer in your phone?

To make use of the magnetometer in your phone to measure the Earth’s magnetic field, we first need to download an app, Phyphox. Scan the QR codes below with your device to download the app.


Phyphox offeres a wide range of tools and experiments for you to learn at the grasp of your hands. Feel free to explore other functions after these activities. Please be careful not to damage your phone or device while experimenting. Please avoid dropping your device on hard surfaces and avoid exposing your device to excessive magnetic fields. The authors of phyphox and SiM committee are not responsible for any damage to your phone.

Launch PhyPhox and select “Magnetometer” on the main menu. Select “ABSOLUTE” and hit play to start detecting.

Place your phone on a table. Pause the measurement to record the absolute magnetic field value and the unit.

What is the value?



Predict where you think the sensor is by selecting one of the boxes on the phone diagram below.




Hit play again on the magnetometer. Take a nail or a scissor (or your mouse, pen, water bottle, keychain, etc.), hold it above your phone at a certain spot, and record the values. Be sure to keep the distance between the magnet and phone the same. Record the values in the boxes below.


Do you observe a change in the absolute magnetic field value near the objects? Compare the values from your results – at what location gives the largest change in the absolute magnetic field?



Based on your results, where do you think the magnetic field sensor is in your phone? On the front? At the back? Which corner would it be? Was your prediction correct?

Type your measured values in the boxes!
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