# Hands-on Activity: The Path of Electrons

### Summary

Students engage in an interactive "hot potato" demonstration to gain an appreciation for the flow of electrons through a circuit. Students role play the different parts of a simple circuit and send small items representing electrons (paper or candy pieces) through the circuit.

### Engineering Connection

Engineers apply their scientific knowledge of electricity, magnetism and light to solving real-world problems that relate to cell phones, computer software, electronic music, radio and television broadcasting, the electrical energy grid, air and space travel, and a wide range of other areas. The electricity we use to listen to the radio or run refrigerators is created at power plants located great distances from where we use it. Engineers use power lines and transformers to move the electricity (electrons) created at the power plant to our homes, schools, offices and stores. Circuits are a way to control the flow of electrical energy in all of these. systems.

### Learning Objectives

After this activity, students should be able to:
• Explain how a simple circuit works.
• Describe the functions of a switch and light bulb as resistors in a circuit.
• List several products that have been engineered to use electrical energy.

### Materials List

For the entire class to share:

• Colored construction paper
• Markers
• Candy (optional)

For a class demonstration of how a circuit works:

• Two D-size batteries
• Small light bulb in a light bulb holder (available at hardware stores)
• Wire to connect the batteries to the light bulb holder

### Introduction/Motivation

Who has heard of a circuit? A circuit is a complete path of electrical energy.
Class demonstration: Create an example of a simple circuit using one battery, wire and a small light bulb (see Figure 1).
Electrical energy is all about charge. Who knows what charge is? Charge is the positive or negative force of an atom or how much electrical energy is in an atom. This gets us back to three main vocabulary words when talking about electrical energy and charge: voltage, current and resistance. Voltage is the amount of energy that can be produced by a charge, current is the flow of charge ( electrons), and resistance is anything that keeps the current from flowing. Today, we are going to talk about simple circuits and how engineers get electrical energy to flow in a current.
Remember that a circuit is the complete path of electrical energy. In the circuit we have created here with the light bulb, wire and battery, the battery provides the voltage and the light bulb gives us resistance, by slowing down the flow of charge and changing it into light. The current flows through the battery, the light bulb and the wires.
What might happen if we disconnect the battery? The light goes off because the current has nowhere to flow. This creates what we call an open circuit. It is like an open circle because there is a break in the line of flow. A closed circuit is like a closed circle or a completed circle. Current can only travel through a closed circuit.
What do you think happens if we add more voltage or another battery?
Class demonstration (continued): Make a circuit using two D-size batteries in series and a small light bulb in a light bulb holder.
Why is the light bulb brighter when two batteries are used instead of one? When we put two batteries together, the power going to the light bulb increases. So, the light bulb gets brighter. Power is how much voltage and current together are getting through the circuit to the light bulb.
Engineers must understand circuits when creating any device that uses electrical energy. Products such as radios, televisions and appliances use complicated circuits to make sure everything works at once. For example, numerous circuits are required for a CD player: to make the CD spin, to play the music and to light up the information screen. And that's just a few of the circuits inside a CD player. Do you think you are beginning to understand what a circuit is and why they are important to engineers? Well, let's stand up and see what you know!

### Vocabulary/Definitions

 The path through which electrical current flows. An electric circuit providing an uninterrupted, endless path for the flow of current. It is like a closed circle or a completed circle. Current can only travel through a closed circuit. Objects that allow the transfer of electrons. The flow of electrical energy; the movement of electrons. A measure of the rate of flow of electrons — how fast they move. Very small, negatively-charged particles. Objects that inhibit the transfer of electrons. A electric circuit that is incomplete, or interrupted at some point. It is like an open circle because there is a break in the line of flow. The product of voltage and current. Objects or substances that prevent the passage of a steady electric current. Amount of energy produced. Related to the force that pushes the electrons.

### Procedure

Before the Activity

• Gather materials and make copies of the What Is a Circuit? Worksheet.
• Using markers, prepare several pieces of paper. Make four pieces with the following words: switch on (closed), switch off (open), battery and light bulb. Prepare enough remaining pieces of paper that say E or electron, for all the students. An alternative that is fun for the students, candy can be used as the electrons (E papers).

With the Students

1. This demonstration involves the entire class. Students stand in a circle to show how a circuit works (see Figure 1). They form a "human circuit."
2. At one end of the circle, identify one student as the battery by giving him/her the piece of paper with the word "battery" on it.
3. At the middle of one side of the circle, identify another student as the "switch." Give this person two papers (switch on and switch off). Have this person begin by holding up the "switch on" paper.
4. At the opposite end of the circle, identify another student as the "light bulb."
5. The rest of the students in the circle are conductors (wire). They each have a piece of paper with a big E marked on it, representing an electron. (Or, alternatively, a piece of candy. No eating yet!)
6. Students start passing the E pieces of paper (or candy) around the circle to the student next to him/her as if they were playing "hot potato." All the students, even the students being the "battery" and the "light bulb," help to move the electrons. Once the exercise is in process, point out how the current of electrons flows around and around the circuit as long as the switch is on (and there is a closed circuit).
7. Next, have the student who is the switch occasionally switch their paper to the "switch off" or open circuit. This action makes a circuit break and the electron papers (or candy) must freeze, or stop moving around the circle.
8. When the switch goes off, the flow of electrons stops, so the current stops. When this happens, the "light bulb" person stops glowing by lowering or "melting down" to the floor.
9. When the student "switch" changes his/her paper to "switch on," the flow begins again and the electrons start moving like "hot potato" around the circle. Because it is turned "on," the student "light bulb" can jump up from the floor and "glow" again.
10. Keep playing the game for a few minutes or until all the students understand how the current (or flow of electrons) moves through a closed circuit (closed circle or when the switch is on). Once they understand, students should know to stop the flow of electrons when the switch is turned off, or the circuit is open.
11. Actively engage all students by re-assigning the roles of the switch, battery and light bulb several times during the activity. See if the students have ideas of other items that could use the flow of energy just like the light bulb.
12. Assign the students the What Is a Circuit? Worksheet. Have them work individually or in pairs. After students finish the worksheet, have them compare answers with a peer or another pair, giving all students time to finish.

### Troubleshooting Tips

To conduct this activity without paper and markers, or candy, have the student hold hands in a circle and ask them to represent the flow of electrons by a gentle "squeeze" of hands that flows from one student to the other, around and around the circle. The circuit breaks when the flow of electrons is not smooth, or when two students next to each other do not hold their hands together.

### Assessment

Pre-Activity Assessment

Vocabulary Review: Have students review the following vocabulary words: voltage (The amount of electrical energy that is able to flow), current (The flow of electrical energy, the movement of electrons), and resistance (Something that keeps the electrical energy from flowing.)

Activity Embedded Assessment

Formation: As a way to actively engage all students and assess their knowledge, re-assign the roles of the switch, battery and light bulb several times during this activity.
Worksheet / Pairs Check: Have students work individually or in pairs on the What Is a Circuit? Worksheet. After students finish the worksheet, have them compare answers with a peer or another pair, giving all students time to finish the worksheet.

Post-Activity Assessment

Class Discussion: Discuss with the students what happened in the activity. Have them come up with ideas in which the same types of closed / open circuit, energy / electricity flow situations are occurring, for example, a light switch or a remote control.
Name Game: Have the students name the following parts of their circuit by asking the students: Which part of our circuit was ________?
• The voltage? (Answer: Battery, because it stored the amount of electrical energy that was able to flow.)
• The current? (Answer: The electron papers [or candy] formed the current moving through the circuit.)
• The resistance? (Answer: There were several resistances, or resistors. The light bulb created resistance by changing the electrical energy into light energy. The switch was a resistance since it could open to stop the current from flowing. And, the students, representing the wire, were also resistors, keeping the current in place.)
• Open circuit? (Answer: The circuit was open when the switch was "off," the circle was broken, and the electrons stopped flowing.)
• Closed circuit? (Answer: The circuit was closed when the switch was "on, the circle was complete, and the electrons were flowing around the circuit.)

### Activity Extensions

Have the students use their imagination in drawing and painting the electrons that they use in the "human circuit."
Have students waiting to join the circuit as "insulators," which break the circuit, causing the light bulb to "turn off," even if the switch is "turned on."

### Activity Scaling

• For younger students, it may be easier to create a class diagram of the human circuit on the board, instead of completing the worksheet.

### References

Dictionary.com. Lexico Publishing Group, LLC. Accessed September 28, 2005. (Source of some vocabulary definitions, with some adaptation) http://www.dictionary.com

### Contributors

Sharon D. Perez-Suarez, Jeff Lyng, Malinda Schaefer Zarske, Denise Carlson