Build a Circuit
A circuit is a path that electricity flows along. It starts at a power source, like a battery, and flows through a wire to a light bulb or other object and back to other side of the power source. You can build your own circuit and see how it works with this project!
What You Need:
*To use foil instead of wires, cut 2 strips each 6" long and 3" wide. Fold each one tightly along the long edge to make a thin strip.)
**To use paper clips instead of battery holders, tape one end of a paper clip to each end of your battery using thin strips of tape. Then connect your wires to the paper clips.
Part 1 - Making a Circuit:
- Connect one end of each wire to the screws on the base of the light bulb holder. (If you're using foil, ask an adult to help you unscrew each screw enough to fit a foil strip under it.)
- Connect the free end of one wire to the negative ("-") end of one battery. Does anything happen?
- Attach the free end of the other wire to the positive ("+") end of the battery. Now what happens?
Part 2 - Adding Power
- Disconnect the battery from your circuit. Stand one battery so that the "+" end is pointing up, then set the other battery next to it so that the flat "-" end is pointing up. Tape around the middle of the batteries to hold them together.
- Set a paperclip across the batteries so that it connects the "+" end of one to the "-" end of the other. Tape the paperclip in place with a narrow piece of tape (do not tape over the metal battery ends).
- Turn the batteries over and tape one end of a paper clip onto each of the batteries. Now you can connect one wire to each paper clip. (The bottom of the battery pack should only have one paper clip - do not connect a wire to it.)
- Connect the free ends of the wires to the light bulb.
(Note: Instead of steps 1-3, you can use two batteries in battery holders and connect them together with one wire.)
In the first part, you made a simple circuit that used a battery to light up a light bulb. Batteries supply electricity. When they're connected properly, they can "power" things, like a flashlight, an alarm clock, a radio, or a timer. Why didn't the light bulb light up when you connected it to one end of the battery with a wire? Electricity from a battery has to flow out one end (the negative or "-" end) and back in through the positive ("+") end in order to work. What you built with the battery, wire, and bulb in step 3 is called an open circuit. In order for electricity to start flowing, you need a closed circuit. Electricity is caused by tiny particles with negative charges, called electrons. When a circuit is complete, or closed, electrons can flow from one end of a battery all the way around, through the wires, to the other end of the battery. Along its way, it will carry electrons to electrical objects that are connected to it - like the light bulb - and make them work!
In the second part, you added another battery. That should have made the light bulb burn more brightly, because two batteries together can supply more electricity than just one! The paper clip across the bottom of the battery pack allowed electricity to flow between the batteries, making the flow of electrons stronger.
Do you see how closed and open circuits work to allow or stop electricity from flowing?
Insulator or Conductor?
Materials that electricity can flow through are call conductors. Materials that stop electricity from flowing are called insulators. You can find out which things around your house are conductors and which are insulators using the circuit you made in the last project to test them!
What You Need:
- Circuit with light bulb & 2 batteries
- Extra alligator clip wire (or aluminum foil wire*)
- Objects to test (made of metal, glass, paper, wood, and plastic)
- Worksheet (optional)
What You Do:
- Disconnect one of the wires from the battery pack. Connect one end of the new wire to the battery. You should have two wires with free ends (between the light bulb and the battery pack).
- You have made an open circuit and the bulb should not light up. Next you will test objects to see if they are conductors or insulators. If the object is a conductor, the light bulb will light up. It is is an insulator, it will not light. For each object, guess whether you think each object will complete the circuit and light up the light bulb or not.
- Connect the ends of the free wires to an object and see what happens. Some objects you could test are a paper clip, a pair of scissors (try the blades and the handles separately), a glass, a plastic dish, a wooden block, your favorite toy, or anything else you can think of.
Before you test each object, guess whether it will make the light bulb light up or not. If it does, the object you're touching the wires to is a conductor. The light bulb lights up because the conductor completes, or closes, the circuit and electricity can flow from the battery to the light bulb and back to the battery! If it doesn't light up, the object is an insulator and it stops the flow of electricity, just like an open circuit does.
When you set up the circuit in step 1, it was an open circuit. Electrons could not flow all the way around because two of the wires were not touching. The electrons were interrupted. When you placed an object made of metal between the two wires, the metal closed or completed the circuit - the electrons could flow across the metal object to get from one wire to the next! Objects that completed the circuit made the light bulb light up. Those objects are conductors. They conduct electricity. Most other materials, like plastic, wood, and glass are insulators. An insulator in an open circuit does not complete the circuit, because electrons cannot flow through it! The light bulb did not light up when you put an insulator in between the wires.
If you're using wires or alligator clips, take a good look at them. Inside they are made of metal, but they have plastic around the outside. Metal is a good conductor. Plastic is a good insulator. The plastic wrapped around the wire helps keep electrons flowing along the metal wire by blocking them from transferring to other object outside of the wires.
To learn more about circuits, visit this Teaching Tip.