Why do I feel electric shock even in the presence of wood? I feel mild electric shock when my laptop with aluminum body is kept on a wooden desk is charging, while both my leg rests on the the leg of the table . Why is that ? Why isn't wood behaving like an insulator here ?
 A: The conductivity of wood depends on its water content. If you're in an arid desert it probably wouldn't conduct electricity, but if it's somewhat humid or the wood is damp for other reasons it's a reasonable capable conductor.
This website says wood can range from rubber to silicon depending on its water content.
A: If the chassis of your laptop is "hot,*" then you would feel a tingle when you touch it even if your body was perfectly insulated from the Earth. That's because the "hot" wire in home electricity supply is an alternating voltage with respect to Earth, and your body and the Earth act like the plates of a capacitor. Each time the "hot" voltage changes sign,** a tiny amount of electric charge flows in to or out from your hand where it touches the laptop. I say "tiny," but it's enough for you to feel it. (Don't ask me how I know!)
* If the chassis of your laptop is "hot," (a.k.a., "live") then that's a serious fault in your home wiring, and you should have an electrician fix it before somebody is injured or killed. If you accidentally touched the laptop with one hand and, for example, a water pipe with the other hand, that could be lethal.
** 50 or 60 times per second, depending on where you live.
