Build a Light Bulb – Circuit Science

Create a battery-powered light bulb from household items

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
  • Scissors
  • Toilet paper tube
  • Mechanical pencil refills
  • Two sets of small alligator clips


  1. 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!
  2. 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.
  3. 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.
  4. Tape the tube with the clips attached to a pie pan so that it stands upright, with the clips facing up.
  5. Carefully clip a mechanical pencil refill between the two alligator clips. The pencil refill needs to be in one piece, so be gentle.
  6. Place a mason jar or clear glass over the top of the toilet paper tube stand.
  7. Touch the other positive and negative ends of the alligator clips to the ends of your super battery.
  8. 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.