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TE Activity: Bulbs & Batteries in a Row

Everyday we are surrounded by circuits that use "in parallel" and "in series" circuitry. Complicated circuits designed by engineers are composed of many simpler parallel and series circuits. During this activity, students build a simple series circuit and discover the properties associated with series circuits.

Electrical engineers are well versed in the logic of parallel and series circuitry. They design complicated circuits that are composed of many simpler circuits as well as special parts that make sure the use of electricity is safe. For example, electrical and mechanical engineers design circuit breakers that are connected "in series" in the wiring of your house. This "switch" automatically breaks the flow of electricity if it rises above a safe level, preventing an electrical overload from damaging your appliances or causing a fire.

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

Grade Level: 4 (3-5)	Group Size: 4
Time Required: 40 minutes	Activity Dependency : None
Expendable Cost Per Group : US$ 4
Keywords: electricity, circuit, series circuit, circuit diagram, resistor, current, light bulb

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Colorado Math
- 1. know, use, describe, and estimate measures of length, perimeter, capacity, weight, time, and temperature; (Grades 0 - 4) [2005]
- 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]
- 2.2 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]

After this activity, students should be able to:

Define, recognize and assemble series circuits.
Explain the path of electrical charge through their circuit.
Understand that when loads (for example, bulbs) are connected in series in a circuit, the total resistance increases.
Describe the function of a switch in a series circuit.
Describe how current changes in a series circuit when a light bulb is removed from or added to the circuit.
Describe how current changes when batteries are added in series or removed from a series arrangement.
Demonstrate the process of measuring using the appropriate units when removing insulation from wires.
Describe the connections among representations of circuit symbols.
Draw series circuits using symbols.
Understand formulas and procedures to solve Ohm's law problems for series circuits.
Use algebraic methods to solve problems involving series circuits.
Apply appropriate computational techniques to solve a variety of problems on series circuits.

Each group needs:

2 D-cell batteries
2 wide rubber bands
3 #40 light bulbs (available at Radio Shack or hardware stores)
3 light bulb holders (available at Radio Shack)
46 in (50.2 cm) insulated wire (gauge AWG 22) (available at hardware stores)
1 basic switch (available at Radio Shack or other electronics stores)
4 Series Circuit Building Worksheets
4 In a Row Math Worksheets

For the entire class to share:

Wire strippers or sandpaper (to remove insulation at wire ends)
Wire cutters
Small standard screwdriver

Note: Most of the materials required for this lab 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 in the class if any of them have strings of the small-sized Christmas lights at home? (Many will answer yes.) Ask the students to brainstorm why it is that if one light goes out on a strand of Christmas lights then half of the strand or the entire strand stops working? (Possible answers: The wire is broken, all of the other bulbs are broken, or the circuit is broken.) Many newer strands of lights have more than one wire linking the lights, as a better way to string the lights together; in this case, if one bulb burns out, the rest of the lights do not go out -- only a section goes out.

A drawing of a man in winter clothing hanging a long string of holiday lights to the outside of his house.

click for copyright

Ask the students if they ever had a flashlight that required batteries? (Many will answer yes.) Then, inquire how many batteries the flashlight needed (Possible answers: One, two, three or four batteries). Ask the students why larger flashlights require more batteries than smaller flashlights? (Possible answers: Some flashlights need more power, some flashlights need more electricity.) Three AA batteries connected "in series" can provide more voltage than a single AA battery. Explain to the students that the holiday lights and the batteries in a flashlight are similar because both are connected "in series." Electrical circuits as well as batteries can be "in series" or "in parallel." During today's activity, we will learn what "in series" means.

Explain to students that electrical and mechanical engineers design circuit breakers to be connected in series with the electrical wiring of your house. The purpose of a circuit breaker is to make sure that too much current does not flow through the electrical wiring in your house and cause equipment failures or a fire. A circuit breaker is similar to a switch; it has an open and closed position. If the electrical current in your house is above a safe level, a circuit breaker opens, creating an open circuit and causing the electricity to shut off.

Background Information on Series Circuits

The current is the same throughout the circuit.
The total resistance for a series circuit is the sum of the resistances of each element.
From Ohm's law (I=V/R), we know that the total current is equal to the voltage divided by the total resistance.
There is a voltage drop across each element in a series circuit that is equal to V=I*R, where V is the voltage of the power source, I is the total current in the circuit, and R is the resistance of the element.
The sum of the voltage drops across each bulb is equal to the voltage of the power source.
The total voltage for batteries linked in series is the sum of the voltages of each battery.
Engineers use switches placed in series to control practically any circuit they make. Just think — most of your electronics have an on/off switch!

Before the Activity

Assemble all the materials.
Cut enough wire for each group: two 6 in (7.6 cm) pieces, one 10 in (25 cm) piece, and one 4 in (10 cm) piece.
You may also want to remove the insulation from the ends of the wires (step 1, below).

With the Students

Using wire strippers or sandpaper, remove ½ in (1.3 cm) of the insulation from the ends of each piece of wire.
Using masking tape, connect two batteries in series. The positive terminal of one battery should touch the negative terminal of the second battery.
Connect the 10 in (25 cm) piece of wire to the positive terminal of one battery using masking tape. The other end of the 10 in wire should be connected to the terminal of one of the light bulb holders. Next, connect a 6 in (7.6 cm) piece of wire to the negative terminal of one of the batteries using masking tape. The other end of the 6 in wire should connect to the switch.
Put each light bulb in a light bulb holder. Finish constructing the series circuit using the parts you have already made, plus a second light bulb holder, the remaining 6 in (7.6 cm) wire, and the 4 in (10 cm) piece of wire (see Figure 1).

Figure 1. The activity setup: A series circuit (left) and the corresponding circuit diagram (right).
click for copyright

On your Series Circuit Building Worksheet, draw a circuit diagram of your circuit. Follow along on the worksheet for the rest of the activity.
Close the switch. What happens to the light bulbs? (Answer: Both bulbs light up.)
Open the switch. Remove one light bulb from its base. Close the switch. What happens to the light bulb in the circuit? (Answer: The remaining bulb stays off.)
Open the switch. Replace the light bulb you removed and remove the other light bulb from its base. Close the switch. What happens to the light bulb in the circuit? (Answer: The remaining light bulb does not light up.)
Open the switch. Make a circuit with three bulbs in series. Close the switch. What happened to the brightness of the bulbs as you increased the number of bulbs in the series circuit? (Answer: The bulbs all got dimmer.)
Use one team's circuit and observe what happens to the brightness of the bulbs as you add a third battery in series. What happens? (Answer: The bulbs all get brighter.)
Use the knowledge you have gained about series circuits to complete the In a Row Math Worksheet. Or, if time is limited, assign the worksheet as homework.

Pre-Activity Assessment

Prediction: Before conducting the activity, ask students to predict:

How many batteries do you think it will take to light the two light bulbs?

Activity Embedded Assessment

Worksheet: At the beginning of the activity, hand out the Series Circuit Building Worksheets. Have students follow along, first diagramming the series circuit they have constructed, then filling in answers as they work through the activity; review their answers to gauge their mastery of the subject.

Post-Activity Assessment

Mental Math Application: Write the equation, I = V ÷ R, on the board. Remind students that this is called Ohm's law. Explain that I = current = flow of electric charge through the circuit (this remains constant through a closed circuit), V = voltage = batteries used, and R = resistance = bulbs used. Challenge the students to explain their team's series circuits in terms of Ohm's law. Have them write the correct letter I, V or R next to the symbols in their circuit drawings. Then, ask the students the following questions:

What happens to the current (I) when we add another battery (V)? (Answer: The current increases.)
What happens to the current (I) when we add another light bulb (R)? (Answer: The current decreases.)
What happens to the current (I) when we have an open switch? (Answer: The current (I) = 0 since no electrons can move through the circuit.)

Series Circuit Advertising: After the activity, ask the student teams what their circuit might be used for? Is it used in a house? Or a toy? Or an appliance? Have the students decide on a name for their circuit and create a magazine ad for their circuit. Suggest they get creative. Have the teams include their circuit diagram and a short explanation of how the circuit works in their ad.

Problem-Solving/Homework: Assess students' understanding of the concepts by assigning the In a Row Math Worksheet as homework.

Use a multimeter to measure the voltage across two batteries in series. How does the voltage compare to the voltage of one battery? (Answer: The voltage of two identical batteries in series is twice the voltage of one battery.)

Use a multimeter to determine the voltage across each light bulb and the current in each bulb. Find the resistance of the light bulb using R=V/I. Then, use the multimeter to determine the voltage across two bulbs in series and the current in the bulbs. Find the resistance of this load using R=V/I. Compare the resistance of one bulb to the resistance of two bulbs in series. (Resistances in series add to give the total resistance.) Compare the voltage across one bulb to the voltage across the battery terminals.

Note: A multimeter is an instrument that combines the measuring capabilities of an ammeter (measures current), voltmeter (measures potential difference, or voltage, between two points) and an ohmmeter (measures resistance) in one instrument to take measurements (current, voltage and resistance) from circuits. Multimeters are available at Radio Shack (or other electronics stores), ranging from $15-$100.

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