Revealing the Science: How Hall Effect Sensors Make Your Laptop Sleep What appears to be a curious trick - placing an AirPods case near a Chromebook and watching the screen turn off - is in fact a straightforward application of the Hall effect. Modern laptops employ Hall effect sensors near the hinge to detect whether the lid is open or closed. A constant current flows through the sensor, and when a nearby magnet is introduced, its magnetic field deflects the moving charge carriers. This deflect