Book 21, Question 119
How Does a Laptop Know When Its Lid Closes?
Close your laptop, and the screen turns off at once. Open it, and the laptop wakes up. There is no button to push, so how does it know?
More fun facts
- For years, laptops and tablets have used a Hall-effect sensor and a magnet to tell whether the lid is open or closed.
- A Hall-effect sensor is a solid-state chip that notices a nearby magnetic field.
- When the lid is closed, everything can be powered off except the sensor and a tiny controller watching it.
- This saves power and lets the computer wake up by itself when the lid opens.
- The same kind of sensor lets a doctor switch on some swallowable medical pills by bringing the north side of a magnet close.
Sources: ti.com
Questions kids ask
Where is the magnet in a laptop?
A small magnet sits in the lid, and a sensor in the base notices it when the lid closes.