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TE Activity: Completing the Circuit

In the everyday electrical devices we use — calculators, remote controls and cell phones — a voltage source such as a battery is required to close the circuit and operate the device. In this hands-on activity, students use a battery, wires, small light bulb and a light bulb holder to learn the difference between an open circuit and a closed circuit, and understand that electric current only occurs in a closed circuit.

Electrical engineers design the circuits and batteries that are in the devices and appliances that we use every day. These circuits can be found in toasters, telephones, microwaves, CD players, DVD players, televisions, video games, medical equipment and, believe it or not, in cars and trucks. Electrical engineers take seriously the responsibility of designing circuits that work dependably and safely.

Learning Objectives
Materials
Introduction/Motivation
Procedure
Attachments
Safety Issues
Troubleshooting Tips
Assessment
Extensions
Activity Scaling

Grade Level: 4 (3-5)	Group Size: 2
Time Required: 20 minutes	Activity Dependency : None
Expendable Cost Per Group : US$ 2
Keywords: battery, circuit, current, electricity, current electricity, resistance, voltage, light bulb, wire, Ohm's law

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Colorado Math
- 1. demonstrate conceptual meanings for the four basic arithmetic operations of addition, subtraction, multiplication, and division; (Grades 0 - 4) [2005]
- 1. reproduce, extend, create, and describe patterns and sequences using a variety of materials (for example, beans, toothpicks, pattern blocks, calculators, unifix cubes, colored tiles); (Grades 0 - 4) [2005]
Colorado Science
- Standard 1: Students understand the processes of scientific investigation and design, conduct, communicate about, and evaluate such investigations. (Grades 0 - 12) [1995]
- 2.1 Students know that matter has characteristic properties, which are related to its composition and structure. (Grades 0 - 12) [1995]
- 2.2 Students know that energy appears in different forms, and can move (be transferred) and change (be transformed). (Grades 0 - 12) [1995]
- 2.3 Students understand that interactions can produce changes in a system, although the total quantities of matter and energy remain unchanged. (Grades 0 - 12) [1995]

Each group needs:

1 D-cell battery
5-7 in (13 - 18 cm) insulated wire (gauge AWG 22) (available at most hardware stores)
1 small light bulb holder (#40) (optional; available at most hardware stores)
1 small light bulb holder (#40) (available at most hardware stores)
Small wire strippers or sandpaper (to remove insulation at wire ends)
Tape (scotch, masking or electrical)
1 Completing the Circuit Worksheet
1 Ohm's Law Math Worksheet

Note: These materials (except the tape and worksheets) can be reused in numerous other electricity activities. When the batteries wear out, dispose of them at a hazardous waste disposal site.

Ask the students: Has your mom or dad ever had you change the light bulb in a lamp? Or, have you ever watched an adult change a light bulb in a lamp or light fixture? (Some students will answer yes.) Why did you change the light bulb? (Possible answers: The lamp would not turn on, the light bulb stopped working.) What happened when the new light bulb was placed in the lamp. (Answer: The lamp worked and the light bulb lit up.)

Tell the students that when a light bulb is broken or burned out, it does not light because the lamp's circuit is open. (Draw an open circle on the board, one that does not connect the end to the beginning). However, when a new light bulb is placed in the lamp, the lamp's circuit is closed (draw a closed circle on the board) and the electrons can move around the circuit and light the light bulb.

Review with students that atoms are made of smaller particles called protons, neutrons and electrons. The electrons carry a negative electric charge and can quickly pass from one atom to another atom within a material. This "flow" of electrons from one end of the material to the opposite end is called current electricity.

Tell students that during this activity, they will discover that a flow of electrons is needed to light a light bulb in a lamp. However, things can happen that will stop the electrons from moving and turn off the light bulb. Ask students to quietly think about what could possibly stop electrons from moving. Explain that they will solve this "mystery" during the activity.

Next, explain to students that electrical engineers design circuits that are in the devices and appliances that we use every day. These circuits can be found in toasters, microwaves, CD players, DVD players, video games and, believe it or not, in cars and trucks. It is the responsibility of electrical engineers to design circuits that work safely and properly. That way, your television will not stop functioning in the middle of your favorite TV show!

Background

Any path through which charges can move is called an electric circuit. If there is a break in the path there cannot be a current (the flow of electric charge), and the circuit is called an open circuit. However, if the path for movement of charge is complete, then the circuit is closed; there can only be a current in a closed circuit. Electrons cannot pile up or disappear in a circuit. A circuit can be as simple as a wire connected to both terminals of a battery, or as complicated as the integrated circuits that are found in a home computer.

A photograph of a D-cell battery with a white wire connecting the positive terminal of the battery to one terminal of a light bulb holder, and a black wire connecting the negative terminal of the battery to the opposite terminal of the same light bulb holder.

Figure 1. An example of a simple closed circuit created using a battery, wire, light bulb holder and light bulb.
click for copyright

Before the Activity

Cut enough lengths of wire for each pair of students.
Make copies of the two worksheets.

With the Students

Ask the students: What is the difference between an open and a closed circuit? (Answer: A closed circuit is a circuit with a complete path, which allows charge to flow [current]. An open circuit is a circuit with a break in the path, so that charge is unable to move.) What is voltage? (Answer: Voltage is the difference in electrical potential between two points in a circuit. It may be helpful to present voltage as the "electrical pressure" that causes the electrons to move in a conductor.)
Have each student team take a battery, a light bulb, light bulb holder and a piece of wire.
Using wire strippers or sandpaper, carefully remove about 1/4-3/8 in (approximately 6-10 mm) of insulation from the ends of the wire.
Try to connect the battery, light bulb, light bulb holder and wire so the bulb lights up. Use tape if necessary. How many ways can you connect the light bulb/light bulb holder to the battery so the bulb lights up? (Answer: None. You only have one wire!)
Now, cut your wire into two pieces. Again, remove about 1/4-3/8 (approx. 6-10 mm) of insulation from the ends of each piece of wire.
Try to connect the battery, light bulb, light bulb holder and two pieces of wire so the bulb lights up. How many ways can you connect the light bulb/light bulb holder to the battery so the bulb lights up? Draw all the ways you found. Try to find at least two ways to do this.
Now, briefly connect the battery terminals with just a piece of wire. What do you notice about the battery and the wire? (Answer: The battery and wire are warm.) In particular, how do your fingers feel as they hold the wire at the battery terminals? (Answer: Students' fingers should feel a little warm.) How do the battery, bulb and wire feel after you have done all the steps in the activity? (Answer: The battery, bulb and wire are warm after doing the activity.)
In pairs, have students complete the Completing the Circuit Worksheet.
(Optional) Working in pairs, have students complete the Ohm's Law Math Worksheet.

Pre-Activity Assessment

Question/Answer: Ask students questions and have them raise their hands to respond. Write answers on the board and discuss as a class.

What is the difference between an open and a closed circuit? (Answer: A closed circuit is a circuit with a complete path, which allows charge to flow [current]. An open circuit is a circuit with a break in the path, and thus, charge is unable to move.)
What is voltage? (Answer: The difference in electrical potential between two points in a circuit. You can think of voltage as the "electrical pressure" that causes the electrons to move in a conductor.)

Activity Embedded Assessment

Question/Answer: Ask students questions and have them raise their hands to respond. Write answers on the board and discuss as a class.

How many connections to the battery are necessary for the light bulb to light up? (Answer: Two. A connection to the positive terminal and a connection to the negative terminal.)
After connecting the battery terminals with just a piece of wire, what did you notice about the battery and the wire? (Answer: The battery and wire were warm.) In particular, how do your fingers feel as they held the wire at the battery terminals? (Answer: Students' fingers should feel a little warm.)
How did the battery, bulb and wire feel after you completed all the steps in the activity? (Answer: The battery, bulb and wire were warm after doing the activity.)

Worksheet/Pairs Check: Have students work in pairs on the Completing the Circuit Worksheet. After student teams finish their worksheets, have them compare answers with a peer group, giving all students time to finish the worksheet.

Post-Activity Assessment

Math Worksheet/Pairs Check: Have students work in pairs on the Ohm's Law Math Worksheet. After student teams finish their worksheets, have them compare answers with a peer group, giving all students time to finish the worksheet.

Drawing and Class Discussion: Have students depict their subject area knowledge gained by sketching and labeling some of the concepts or activities. For example,

Have each group write their own definitions for closed and open circuits. Next to each definition draw a circuit — with one bulb, one battery and wire — that is either open or closed.
Ask each group to draw as many unique ways to construct a closed circuit with only one bulb, one battery and one piece of wire, as they can. Compare the groups' results as a class and discuss the validity of each drawing.

Integrated Teaching and Learning Program, College of Engineering, University of Colorado at Boulder Xochitl Zamora Thompson, Sabre Duren, Joe Friedrichsen, Daria Kotys-Schwartz, Malinda Schaefer Zarske, Denise Carlson © 2004 by Regents of the University of Colorado.
The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0226322. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.

Last Modified: April 27, 2006