Quote Originally Posted by deano View Post
another example is that a switch acts as a door if you open it lets you to walk through ..when its closed you cant walk through
Err...that's backwards. An "open" switch is one whose electrical contacts are open, e.g. not touching, and does NOT allow current to pass through. When the switch is "closed", the two sides of the switch are electrically connected, and allow current to pass. It's more like a drawbridge: in the "open" (up) position, nothing can pass, while in the "closed" (down) position, traffic can flow across the bridge.