How does laptop knows the lid is Closed or Open?

[VivekK]

I just had a random question in my mind... I close the Lid of my laptop for sleeping mode and to wake up I lift up the lid but How does my Laptop know the lid is closed or open. As far I know there is no proximity sensor on the screen so What's the mechanism behind this??

[Theguywhobea]

There is probably a little switch or something inside the hinge mechanism, when you close the lid it presses the switch.

[Wyo]

Some laptops have a switch that opens and closes when the screen is open or closed. On fairly new laptops they use magnets that are usually hidden in the frame somewhere in the LCD panel that controls that stuff. 

[Dujith]

Almost all of the time its a magnetic switch that reacts to a magnet in the bezel.

You can try this out by getting a magnet (small one is enough) and move it around your laptop surface.

 

And dont worry this is not a troll attempt to kill your laptop