The ans is - A Piston
I'm small and sometimes worthless. I sit there and look at you as you pass me by. I cannot move but I wish I could. If I'm found, it's a good thing but only if I can see you. What am I?
I am always trapped in a glass cage.
I usually just sit at the bottom of the cage,
But I climb higher when I get hotter &
Climb down when things get cooler.
What am I?
