Question

I am confused. Can someone please help me with this as quickly as possible?

Answer 1

a. See below.
b. Convenience - see detail below.

Explanation:

As drawn the switches are in position for lighting the bulb. The battery output voltage, `v_"out"`, is routed so that the the voltage across the bulb is `v_"out"`.

a. Now, throw a switch, let us say you throw `S_1`. Suddenly the wiper of `S_1` does not connect to the + side of the battery. The wiper goes to node B which is not connected to anything except some wire which does not connect to anything. The circuit is open. Therefore the bulb has 0 V across it and is not lit.

Now the instructions say to move each of the switches to a new position. So you have to throw `S_2`. `S_2's` wiper goes to node D. Well now, wire BD makes the + side of the battery connected to the bottom (as drawn) of the bulb and the bulb lights again.

b. What good is that arrangement in the home. Assume your bedroom is at the far end of a long hallway. There is a bulb on the ceiling in the middle of the hallway. It would be nice to be able to turn on the bulb from either end and than turn it off from the other end. Ta-da! This circuit will allow you to do that.

I hope this helps,
Steve