Which way does it go???

    Every year, it is the same old thing at Christmas time.  I have to spend hours trying to get the lights to work correctly.  Some of the strings of lights light right up when you plug the string in.  BUT! there are always a few of the strings that just won't light up.  You have to go through and check each and every lightbulb in the string until you finally get the lights to light up.  If you are lucky, you can see where a bulb is missing and all you have to do is replace it.  Usually though, one of the bulbs is just loose and needs to be tightened up to get the string to work.  These Christmas lights that give us so much trouble use a special kind of circuit called series circuits.  In a series circuit, the electrons flow through every device in the circuit.  There is only one pathway for the electrons to follow. The electrons go through one device after the other, sort of like running the bases at a baseball game.  Most of the circuits that you have made during our class exercises have used series circuits.  That is why if any one wire came loose, then the whole circuit would quit working.

1.  Two 1.5 volt batteries add together in series to give us 3 volts going into the light.  What would happen if any of the wires were disconnected?  Yes, write your answer!

Again we have two 1.5 volt batteries in series giving us 3 volts, but we have two bulbs so each is getting only about 1.5 volts.  These lights will not be as bright as in "A".

In a series circuit, the voltage adds up but so does the resistance.  Remember Ohm's law,  if resistance increases, current decreases.  When we add devices to a series circuit, each device gets less current. Remember, the voltage of two or more batteries will add together. Two batteries in a series circuit will give you 3 volts. Two batteries in a parallel circuit will still give you 1.5 volts.

Did you ever notice that baseball games tend to have very low scores and that basketball games can have pretty high scores? Of course you did! Let's think about this for a moment. In baseball, like we mentioned above, there is only one pathway for the scorer to follow. If anyone stops the scorer, then the play is over. In basketball though, the scorer can take many different paths. If anyone stops one path, then there is always another path that the scorer can send the ball down. There is an electrical circuit that works like a basketball game. We call it a parallel circuit. In a parallel circuit, there are several different pathways for the electrons to follow. If one pathway is blocked then the electrons can go down a different pathway.

2. Question: Does the electricity in your home act more like a baseball game or a basketball game? YES!, I want you to write your answer down on paper. HINT!!! If someone turns a light on or off in the kitchen, is the light in your room affected.