Experiment Details

• Grade Level: 3rd–6th Grade (adaptable for K–8)
• Key Topics: Electricity, Circuits, Energy Transfer
• Estimated Time: 30 minutes
• Mess Factor: Very Low

Purpose: To learn how electricity flows through a closed circuit and powers a bulb, using household materials.

Hypothesis: If we connect the battery and bulb in a complete loop with wires, then the bulb will light up because electricity can flow through the circuit.

Step-by-Step Instructions

1. Prepare the wires: If your wires aren’t already stripped, have an adult use scissors to remove about ½ inch of insulation from both ends of each wire. Explain to your child that this exposes the metal, which allows electricity to flow.
2. Connect the battery (positive side): Tape one end of the first wire securely to the positive (+) end of the battery. Ask your child to notice the markings on the battery and practice identifying positive and negative.
3. Connect to the bulb: Attach the other end of the same wire to the metal base of the bulb (the small metal tip on the bottom). Tape it so it stays in place, and encourage your child to observe how metal-to-metal contact matters.
4. Complete the bulb connection: Tape one end of the second wire to the side of the bulb (the threaded metal part). Ask your child to describe the path electricity is taking so far.
5. Connect to the battery (negative side): Attach the other end of the second wire to the negative (–) end of the battery. Secure with tape, making sure all connections are tight.
6. Test the circuit: Ask your child, “What do you predict will happen?” When all the connections are made and the circuit forms a loop, the bulb should light up! If not, check all connections and be sure the wires are touching metal at each point.
7. Break the circuit: Gently disconnect one wire and observe what happens. Guide your child in noticing that the bulb turns off when the circuit is broken—there’s no complete path for electricity.
8. Try a switch: Show your child how to use a folded piece of aluminum foil as a simple switch. Place the foil between a wire and the bulb’s metal side; open and close the circuit by touching or removing the foil. Ask, “Why does the bulb turn on and off?”
9. Draw a diagram: Invite your child to sketch the circuit they built. Label the battery, wires, and bulb, and use arrows to show how electricity flows in a loop.

Results & Scientific Explanation

When your child completes the circuit by connecting the battery, bulb, and wires in a closed loop, electricity flows from the battery’s positive end, through the wire, into the bulb’s metal base, across the filament, and back to the negative end of the battery. This flow of electric current makes the bulb light up! If any part of the circuit is disconnected, the flow stops and the bulb turns off. The aluminum foil “switch” lets your child experiment with opening and closing the circuit, introducing the real-world concept of how switches work in homes and electronics.

• Closed circuit: All connections are secure and electricity flows—the bulb lights up.
• Open circuit: There’s a break in the path, so electricity cannot flow and the bulb stays dark.
• Switch: A device (like foil) that opens or closes the circuit, controlling whether the bulb is on or off.

Teaching the Why: How Circuits Work

Electricity always seeks a complete path from the power source, through a load (the bulb), and back to the source. This is called a closed circuit. If there’s a gap or break—a wire not connected, a switch turned off—it’s called an open circuit and electricity can’t flow. Most household electronics, lamps, and even cars work on the same principle!

Real-Life Connections

Encourage your child to look for circuits at home: light switches, remote controls, even battery-powered toys. Understanding simple circuits lays the foundation for more advanced learning about energy, electronics, and technology.