I Didn’t Think the Kids Could Make This Work, But…

I have been teaching my kids about circuits lately.  They have been using the little 1.5 volt incandescent bulbs, wires with alligator clips, and D cell batteries.  D cell batteries are also 1.5 volts.  I had brought in every lightbulb in my house that had burned out so the kids could see all of the filaments floating around in the bottom of the bulb.  I also brought in one working 40 watt incandescent bulb.  I thought it would be fun for them to see if they could get the bulb to light.  Because the bulb says 120 volts on the bottom, I didn’t think the students could get it to work.  We had a limited number of batteries to even try to light the bulb.

I put the large light bulb in a station for free experimentation.  I thought the kids had forgotten about trying to get the large bulb to light, so I put the bulb in my lamp.  When they asked about trying to get the bulb to light again, I took it out of the lamp and told them they could try up to seven batteries.  They tried the seven batteries and the bulb didn’t light.  When they were puzzled, I asked them whey they thought it didn’t light.  Showing the girls the print on the bottom of the bulb and inquiring about the voltage of the battery, they realized they needed more batteries.  I explained to them that we probably didn’t have enough batteries.  Their reply was, “PLEASE, PLEASE, PLEASE, can we try more batteries?!”  Since they were so persistent, I let them.  I expected there to be no change in the bulb.

About five minutes later, I hear the girls squeal with delight!  You guessed it!  They lit up the bulb!  They had about 21 D batteries taped together end to end with masking tape down the length of them.  By this time in class, about five or six students had joined in and were holding a section of the batteries to make sure they were completely touching end to end.  One child was holding the wire from the positive to the negative end of the batteries.  When they got the bulb to light a little, they wanted to add more batteries to make it brighter.

What’s even better?  With a tiny bit of prompting, the kids were doing real world decimal addition/multiplication.  They were counting the amount of volts they had on each battery and figuring out how much voltage they were using to power the light bulb.  I am glad I gave into their pleading and never told them I didn’t think it would work :)!  They will probably remember this MORE than anything I had planned to officially teach them!