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.
- 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)
- 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)
- 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)
- spectacular results Review by al domz
Me and my group mates presented to our class as part of our simple process demonstration. Everyone was amazed by our presentation. Instead of the d size batteries we used the square battery of a spot light....it really worked and the pencil lead was actually really hot..one of my group mates touched it out of curiosity and got a small burn...i already warned him but he did not listen...anyways the presentation was successful.
(Posted on July 19, 2012)
- Perfect Timing! Review by Amy Lyttle
I have just started teaching electricity and this will be a fantastic demo to add to my lesson!
(Posted on March 14, 2012)
- Brand Matters Review by Sarah
We tried this experiment with different batteries and different brands of lead. We found that Duricell batteries worked the best and the Pentel HB lead worked the best.
(Posted on April 9, 2013)
- 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)
- 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)
- Amazing Experiment!!! Review by Sam
My 10 year old niece loved it! I do have some suggestions -
1. Make sure your batteries are tightly connected. We did a test with a small fan to make sure the batteries were connecting. We even used two rules to make a splint to ensure the batteries remained in a tight formation.
2. We found it worked best with .9mm pencil refills. .7mm and .5mm also had good results but .3mm broke immediately on contact.
We used Pental brand refills available at Staples.
I would guess that those having trouble are not connecting the batteries together tightly.
(Posted on May 3, 2013)
- It worked! Review by Mrs. A
When I pushed tightly with the clips against the battery ends, the lead broke immediately. But when I barely made contact with the clips and the batteries it worked perfectly. The graphite glowed brightly for about 15 seconds. Very little smoke, but I used C batteries which might have made the difference. I tried it with 0.7 mm lead and it would not work. Great demonstration!
(Posted on March 22, 2012)