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Summer Brain Games

Experiment: City Circuit

Almost everything in the city uses electricity. Build a simple electric circuit from aluminum foil and a string of holiday lights to learn about what conducts electricity and what doesn't.

Instrucciones en Español


Aluminum foil
Single LED light, or one light from a string of holiday lights (note: the string of lights may no longer work when you disconnect one light)
Wire strippers (if using a string of holiday lights)
Glue stick
Clear tape
Circuit template (PDF)
3V button battery
Items to test for conductivity like buttons, paper clips or toothpicks


  1. Cut several strips of aluminum foil that are about ¼-inch wide. They do not have to be exactly measured. The strips of aluminum foil should be a little bit longer than each of the segments of the square circuit template on the next page.
  2. For each segment or side of the circuit template, glue the foil down to create the circuit. Lay the foil on paper and rub the glue stick on one side of the foil, making sure to go all the way to the ends. Then pick up the foil, turn it over and stick it on the template. Make sure there are no gaps between pieces – the foil pieces should make a complete square.
  3. If you’re using a light from a string of holiday lights, cut it off the string along with a couple inches of wire on either side. Use the wire strippers to expose the copper wire at the ends. If you’re using a single LED light, gently bend the wires so they stick out sideways from the bulb.
  4. Use clear tape to connect the wires to the aluminum foil in the spot indicated on the template. Make sure the metal is touching the foil and is securely held down with tape.
  5. Place the battery in the circle and fold the corner over so the other circle lines up with the top of the battery. The foil should be in direct contact with both sides of the battery. If all of the connections are good, the bulb should light up!
  6. Test different objects to see if they conduct electricity. Cut the circuit as indicated on the template. Place the items that you’re testing on both sides of the cut circuit. If the object conducts electricity, the light will light up! 

What's Happening?

An electric circuit can be as simple as a flashlight or as complicated as a city power grid. A simple circuit contains a power source (battery), wires, switch and a load (light bulb). The word “circuit” sounds like “circle,” and a circuit needs to be circular, or connected, to work. A complicated city power grid uses an electrical generator to produce very strong electrical currents. The electricity travels along metal wires to where it needs to go. On its way, it needs to be stepped down, or weakened, before it can safely power your electronics. The wires connect the power source to the devices and back again. Think of your phone or microwave as the light in the circuit that you just made. This creates the path for electricity to travel. If there is a gap or break in the path, the circuit isn’t complete and the light won’t turn on.

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