Saturday, March 8, 2014

Conductive Materials (aka Making a Bulb Light Up!)

I made the mistake of trying to Science after a LONG nap on a partially empty tummy!  Lesson learned; after dinner is just as good of a time for Science Saturday as any...

First, the science.

This week, I shouldn't be straining anyone's brain.  Metals have a property in common; they give up their electrons pretty easily.  In a dry cell battery (think AA, AAA, C, etc.), there are two metals.  Each gives up its electrons differently.  Some do it more easily than others.  This difference is called electronegativity.  We take advantage of this difference by separating the two metals and forcing the electrons to move through wires that we connect from one side to another.  As the electrons move, we can put something in the way, which causes an energy change.  The most simple version of this is a light bulb filament.  As the electrons move through the filament, they encounter resistance, and give off light and heat.  Ultimately, the electrons return to the other side of the battery.  The battery 'dies' when all of the metal on one side is finished reacting, and has given up all of its extra electrons.

The wires that the electrons travel through are made of metal.  Remember that metals like to give up their electrons.  So when they encounter an electron 'push' from one side of the battery, the electrons march down the wire, replacing the one that has moved in front of it.  Materials that are note metal hold on to their electrons too much to have them get pushed.

Got it?  Just don't stick your fingers in an outlet, and you'll be OK.  More importantly, the fashion report.  SK decided that she needed her Doc McStuffins lab coat today, but we couldn't find it.  We figured it was probably in the wash.  She settled for her Minnie Mouse ears (happily) and the safety glasses.

I got a 6V lantern battery, some aligator clip wires and a small LED bulb.  I spent less than $10 on the setup, but you could dissect an old flashlight, and probably accomplish the same experiment.  I connected the wires to the battery and bulb in a circuit.  We talked about the electrons moving around the path.  SK traced the path with her fingers.  I disconnected the battery "Hey, you turned the light off!"  We traced the path again, and wouldn't you know it...the path was broken.

I also cut one of the wires open, so we could see what was inside.  I asked SK to describe the inside.  It looked like: thread, shiny, and sharp.  I asked what else could be shiny and sharp...she didn't quite pick up what I was putting down.  I grabbed a kitchen knife; both shiny AND sharp.  What is it made out of?  Metal!

To complete the broken path, we needed metal!  She suggested we try the knife.  Light bulb = on.  I suggested a paper clip.  Light bulb = on.  She suggested her magic fairy wand.  Light bulb = off.  We tried to figure out what it was made of...sure wasn't metal!  We tried a glass bottle.  Light bulb = off.  Lastly, we tried her necklace.  Light bulb = on.  That was about all SK had in her.

But wait!  "Daddy, can we do the one with the food coloring and water!  I want hot water because it went SO FAST!"  So we finished the night mixing colors.

Your homework:

  1. Find some things to connect to a battery.  What could we use other than light bulbs?
  2. How did you describe electrons to your SK?
  3. Did anything conduct the electricity that surprised you?

Time to Science!