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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!
*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:
Part 2 - Adding Power
(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?
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!
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.