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.
- 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)
- Nice Activity, Chance to Experiment Review by Bill Polacheck
I used this activity early on in my electricity unit in sixth grade. I did it under an exhaust hood out of fear of tripping smoke alarms, but I don't think much smoke would have escaped. I initially tried using two six-volt lantern batteries tied together but it didn't work. Any idea why?
(Posted on March 15, 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)
- Type of pencil lead is important Review by Ruth TenBroek
I'm preparing for a science class on electricity, so my boys and I tried building the light bulb. The graphite kept breaking without glowing at all(we used Pentel brand Super Hi-Polymer Lead). I went back to the store and bought a different brand(Papermate), and it worked perfectly!!
(Posted on March 21, 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)
- great Review by MILE
tHIS PROJECT IS LEGIT
(Posted on April 25, 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)
- 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)
- 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)
- 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)