Build a Light Bulb - Circuit Science
When you are conducting experiments and demonstrations using electricity, you'll use the science of circuits. Amazing things are possible with circuits including alarms, radios, and lights. In the Build a Light Bulb experiment, you'll use household items to construct a complete circuit that results in a homemade light bulb.
- Eight D-sized batteries
- Mason jar or other clear glass
- Electrical tape
- Pie pan
- Toilet paper tube
- Mechanical pencil refills
- Two sets of small alligator clips
- Using electrical tape, fix eight D-sized batteries together, end-to-end, with the positive ends connected to the negative ends. You've made a super battery!
- Use scissors to cut a toilet paper tube to a height that will fit comfortably (leave plenty of room) inside of a mason jar or other clear glass.
- Tape one positive and one negative alligator clip to one end of the toilet paper tube. Make sure the clip is facing up, away from the rest of the toilet paper tube.
- Tape the tube with the clips attached to a pie pan so that it stands upright, with the clips facing up.
- Carefully clip a mechanical pencil refill between the two alligator clips. The pencil refill needs to be in one piece, so be gentle.
- Place a mason jar or clear glass over the top of the toilet paper tube stand.
- Touch the other positive and negative ends of the alligator clips to the ends of your super battery.
- Give the circuit a moment to circulate the electricity and… voila! The pencil refill begins to glow.
How Does It Work?
When you touch the free ends of the alligator clips to your "super battery," you form a complete circuit. That means electricity flows freely through the entire apparatus that you have just built. This flow of electricity channels through the graphite-based mechanical pencil refill that is connected by alligator clips. The flowing electricity has a noticeable effect on the pencil refill. The thin refill begins to glow and give off smoke. This happens because the electricity heats the graphite refill to an incredible temperature. So, if you are hoping to save some money by using your own homemade light bulbs around the house,stick with the store bought ones. It's not as cool, but it is safer.
- Lightbulb Experiment Review by Dawn Hardy
My second graders used .7mm leads and the experiment worked beautifully! We actually did the experiment a few times using different battery combinations with interesting results. There really is a difference in brands. This was great!
(Posted on May 17, 2012)
- great Review by Eva
just like the bulb in the microwave experiment, this is great. We are so accustomed to ordinary bulbs, it is great fun to see the variations on the everyday reality.
(Posted on March 14, 2012)
- impressive, but hard to get to work Review by Science lover
10 of the 12 pencil leads we used broke immediately with a puff of smoke. Only two worked (for about 10 seconds). It was impressive, but it would be a good idea to buy extra pencil leads. I will also try thicker ones next time also, to see if that makes any difference
(Posted on March 16, 2012)
- Light bulb review Review by Ami
Awesome! Is the smoke from the graphite burning as it is conducted through the resisting filament until the oxygen is used up? Then it glows! It sure takes a lot of energy for this light bulb!
(Posted on March 14, 2012)
- Students were DEFINITELY engaged!!! Review by Lydia
My 6th-8th graders loved this experiment. After doing the 0.5mm lead their curiosity had them trying their own 0.7mm...and wondering if adding one more battery would help. I just attached insulated wire to some cheap alligator clips from RadioShack (I bought 2 types: the cheaper all metal ones actually worked better than the slightly nicer ones with insulated grips since the teeth were not as sharp, therefore breaking the lead less). The clips did get hot when doing it multiple times in a row, but this just shows that the energy is converted to multiple forms including light (EM) and heat (thermal). A previous review said Pentel lead didn't work, but it worked for my class.
(Posted on April 20, 2012)
- WOWIE Review by Cail
Wow, i did this experiment times, it worked 8 times and i was very impressed. the thiker the lead, the better it works!!
(Posted on May 21, 2012)
- Question Review by Student
I tried it and it did work, but have a question, how does the energy transfer through the lead? Or why does it transfer?
(Posted on March 26, 2012)
- It was amazing! Review by Gwen W.
We used a 6v latern battery and it worked great! It burned for a long time! It's so cool!
Julia, age 9
Alex, age 6
(Posted on March 4, 2013)
- didn't work despite troubleshooting Review by Cristy
I could not get this to work. I did not have D batteries around, but I tried it with 8 or 9 C batteries, 1 or 2 big square lantern batteries, 8 and 16 AA batteries... basically lots and lots of battery combinations. I would see smoke, but now glowing. I tried a little motor between the clips to make sure my circuit was good, and it was fine. Tried with a jar and without a jar, even tried replacing the O2 in the jar with CO2 via vinegar/baking soda gas "poured" in to it. Put some Nichrome wire between the clips and got a little glow, but just orange wire. Nothing impressive. I would test this in advance to not end up with disappointed kids. I am a pretty disappointed 40-something!
(Posted on November 5, 2012)
- Lots of Trial and Error Review by Richard Moore
I noticed the first reviewer had trouble getting this to work. I did as well. I went back and forth to the office supply store to buy various brands and widths of lead. Still didn't work! After 3 hours I simply gave up.
The next morning before school I taped together 10 D batteries, made sure my wires were conducting, used Papermate .5mm lead, used new tight alligator clips, and a much smaller jar. Worked perfectly! I used .7mm as well. Then I used a very thick lead shaved from an HB pencil. It took 18 volts, but worked. Couple this with Time Magazine's Man of the Year article on Thomas Edison and you've got a pretty good lesson in reading, critical thinking, and of course, science.
(Posted on December 11, 2012)