Laptop mousepad question?

[Phantaxus]

I have access to several laptops with those little mousepad thingys that let you move the pointer with you finger. Yesterday I observed something strange. If I use something that is not my finger (pen, screwdriver etc..) it will not work ah I thought someone on answerbank will know why. Over to you...

[banana]

Ooohh .Phantaxus ..Ive just tried all sorts of things that come to hand in a living room.An earing laid flat,a small statue of Buddha( head end),a cork,flat thingumajig for poking fingernails all resulting in no movement. But a 1919 penny works!.Im thinking its something to do with the spread of pressure on the pad(hence the choice of objects originally) and maybe heat(?) since the penny id very thin. But interesting anyway.

[SoupNazi]

As you finger touches the pad, it completes an electrical circuit to Earth creating a resultant reaction in the mouse-pad. This explains why any other non-conducting object has no effect.