1. Activate students’ prior knowledge about electricity.

Find out what students already know about electricity. Encourage them to identify objects in the room that use electricity. Ask: Do you know how electricity travels to power these devices? (Electricity travels through circuits.) Ask: How is electricity used in more complicated projects, like powering a robot? Explain that electricity is used to provide power to various parts of the robot, such as moving mechanical parts, systems that provide control for the robot (like the CPU), and data-gathering components (like sensors).

2. Introduce the concept of a circuit.

Draw a circle on the board. Ask: Is the shape open or closed? (It is closed.) Now draw a circular shape that is not complete, like a “u,” on the board. Ask: Is this shape open or closed? (It is open.) Inform students that in order for electricity to flow and power a device, there must be an unbroken, or closed, pathway. Do a quick demonstration using the room’s lights. Flip the light off in the classroom. Tell students when the light goes off, the circuit is open and electricity cannot reach the bulb to produce light. Reference the shapes previously drawn on the board. Flip the light back on. Tell students the circuit is now closed and electricity is free to travel and illuminate the bulb.

3. Students build a simple circuit to light a bulb with the help of a diagram and demonstration.

Tell the class they will now build a closed simple circuit to light a bulb. Show the class the separate pieces they will use: a D cell battery; the holder for the D cell battery; four alligator clip leads; a 2.5 volt, 0.2 amp, or smaller bulbs with a screw-type base; and two bulb holders. Separate the class into working groups of 2-4 students and distribute the parts listed above to each group. Explain that their group goal is to work together to build a simple circuit that will light the bulb. Explain that you will demonstrate how to build a circuit and they will follow along, but later on they will need to work in their groups to build a circuit on their own. Draw a simple circuit diagram on the board, and label and explain all of the parts, using the provided diagram. Walk the class through building the circuit using the How to Build a Simple Circuit handout.

After groups have successfully lit the bulb, have them make a labeled sketch of the circuit they built in their notebooks. Ask: What would happen if a switch were added to this circuit? Provide each group with a single knife switch and have them update their circuit. Elicit answers from students that help them make connections between the closed circuit they just built, and the earlier demonstration with the classroom light that creates an open and closed circuit. Update the diagram you previously drew on the board to include a switch using the Simple Circuit with Switch diagram provided.

4. Students build series and parallel circuits in small groups.

Ask students to remove the knife switch from their circuit, so they have a simple circuit again. Ask the class to predict what will happen if an additional bulb is added to the simple circuit, without making any other changes. (Again, the knife switch should no longer be included in the circuit.) Have students record their predictions in their notebooks. As students are making predictions, give an additional light bulb and bulb holder to each group. Then, allow groups time to experiment with lighting two bulbs on a single pathway. Remind groups of what a single closed pathway is by drawing attention back to the diagram on the board and the first circuit they built. Facilitate as needed. Use the provided How to Build a Series Circuit handout that contains a diagram to check student work.

After they have successfully built their circuits, tell students that this type of circuit is called a series circuit. It has a single pathway from the energy source (battery) through a series of loads (bulbs) and back to the energy source. Ask: What happened when a second light bulb was added? Explain that the bulbs are dimmer because the additional bulb slows the flow of electricity in the circuit, causing the lights to dim. Ask: What might happen with the addition of a third bulb? Explain they could expect the bulbs to be even dimmer or not light at all. Ask: What would happen if a component in the circuit is disconnected or if there is a broken bulb in this circuit? (The circuit will be open and none of the bulbs will work.) Have students make a labeled sketch of their series circuit in their notebooks and record their observations about building this type of circuit.

Pose the following question to the class: If one bulb in your circuit went out, what would be necessary in order for the other bulb to remain lit? Explain that the configuration of the circuit must change so bulbs are on separate closed pathways with the energy source. Allow time for groups to experiment with building a circuit that lights both bulbs, with the additional challenge that one bulb must remain lit when a single component is disconnected within the circuit. Facilitate as needed. Use the provided How to Build a Parallel Circuit handout that contains a diagram to check student work.

Explain that this type of circuit is called a parallel circuit, where bulbs are connected on separate pathways. Each bulb in a parallel circuit will be equally bright, but will drain the battery at an accelerated rate. Have students compare and contrast the working models of parallel circuits created by each group. Ask: Were all the groups’ parallel circuits the same? Have students make a labeled sketch of their parallel circuit in their notebooks and record their observations about building this type of circuit.

5. Review the different types of circuits.

Review the similarities and differences between the four different types of circuits that students discussed during the activity: open, closed, series, and parallel. Have a discussion about the applications of each type of circuit.

Give students the example of street lights being configured in parallel circuits. Remind the students that in a parallel circuit, the current to each load, like a bulb, is separate, so if one bulb burns out, the others will still work. Ask the class: Why would this be useful? (Because if one light goes out, the rest will stay on, ensuring the safety of people on that street.) Encourage students to share other applications in everyday life.