LESSON 7 Closed Circuits and Light Bulbs Nagele, et al. 2016 page 80

LESSON 7 Closed Circuits and Light Bulbs Overview Students explore how a light bulb works and learn the difference

between compact fluorescent (CFL), incandescent, and light emitting diode (LED) light bulbs. Students will imitate engineers by using their new knowledge to problem solve by building a homemade flashlight.

Student Learning Targets

• I can compare CFL, LED, and incandescent light bulbs and give you advantages of each.

• I can make decisions based on consumer information when making choices for my home lighting; and I can give you reasons for my decisions.

• I practice my problem solving skills in making a flashlight.

NGSS MS-PS4-2. Develop and use a model to describe that waves are reflected, absorbed, or

transmitted through various materials. [Clarification Statement: Emphasis is on both light and mechanical waves. Examples of models could include drawings, simulations, and written descriptions.] [Assessment Boundary: Assessment is limited to qualitative applications pertaining to light and mechanical waves.]

Background Transmission lines and appliance electrical cords are made of conducting metals. In many appliance cords, there are actually two wires, each composed of many metal strands. The two wires are necessary so that a complete circuit can be created, beginning at the power plant, following the wires to our homes at the outlet, into the appliance, and back to the power plant. One wire in the appliance electrical cord conducts electricity to the load (such as a light bulb or motor) and the other conducts electricity from the load back to the electrical outlet in the wall.

The load the students have been using in previous lessons is an

incandescent light bulb. If you look closely at a light bulb, you will see two small wires with a filament (the wire that lights up) in between. A light bulb only works if there is a complete circuit. If you were to remove the metal base of the bulb you would see that one of the two wires in the bulb connects to the side of the threaded metal base, and the other to the tip of the metal base. The tip and the threaded base are separated by an insulating piece of ceramic to prevent short circuiting. The only way to make the bulb light is to make sure that the electrons have to get through the bulbs to get back to the battery. When the electrons go

LESSON 7 Closed Circuits and Light Bulbs Nagele, et al. 2016 page 81

through the metal tungsten filament, they cause the filament atoms to vibrate with excitement, giving off heat and light (atom movement converted into heat and heat into light energy). To make the electrons go through the filament, you must make sure that the filament is part of the circuit. To do so, one part of the circuit touches the side (screw side contact) of the metal base, and another part touches the very bottom of the light bulb (electrical foot contact). See illustration below.

Overhead 1 – From: Harris, Tom. "HowStuffWorks "Light Bulb Structure"" HowStuffWorks "Home and Garden" Web. 03 Jan. 2012. <http://home.howstuffworks.com/light-bulb1.htm>.

Compact florescent light bulbs or CFLs, use a mercury gas to produce a glow from excited electrons. Instead of a glowing filament, CFLs are glass filled with mercury and argon vapor. When an electric current passes through the vapor, it excites the electrons in the atoms of gas vapor producing ultraviolet light. The ultraviolet light then stimulates the fluorescent coating painted on the inside of the glass bulb. As the coating absorbs the ultraviolet light energy, it emits visible light. While energy from CFLs is converted into more light and almost no heat, making CFLs more efficient sources of light than incandescent bulbs, the mercury in CFL bulbs is extremely toxic. Thus broken and discarded bulbs can result in human injury and environmental degradation. For more detail on CFLs, visit http://science.howstuffworks.com/environmental/green-tech/sustainable/cfl-bulb.htm. Light emitting diodes or LED bulbs, contain one or more diodes that transform electronic current to light energy. LEDs do not have a glowing filament or gas. The LED bulb is illuminated by the movement of electrons in a semiconductor material. The diode is a device that contains a semiconductor material (a poor conductor that has atoms of another material added to it to create an imbalance of electrons) in layers with an electrode at each end. Layering of materials, some with more electrons than others causes movement of electrons from one layer to another when voltage is applied in a circuit. LEDs are just tiny

LESSON 7 Closed Circuits and Light Bulbs Nagele, et al. 2016 page 82

light bulbs in a circuit. They give off light (energy) particles called photons when the electrons in the atoms of the semiconductors jump from one orbit to another around their atom. LEDs are commonly used in everyday life today including to form numbers in digital clocks, transmit information from remote controls, in Christmas tree lights, and even to form images on a television screen. For more information on LEDs visit http://www.howstuffworks.com/led1.htm.

http://hackadaycom.files.wordpress.com/2013/10/led-low1.jpg

Vocabulary compact fluorescent (CFL), incandescent, and light emitting diode (LED), filament, diodes, photons, voltage, semiconductor, wattage, lumens, load.

Resources How stuff works – an article that describes how an incandescent light

bulb works: http://home.howstuffworks.com/light-bulb2.htm Compact florescent light bulbs or CFLs –

http://science.howstuffworks.com/environmental/green-tech/sustainable/cfl-bulb.htm

LESSON 7 Closed Circuits and Light Bulbs Nagele, et al. 2016 page 83

Light emitting diodes or LED bulbs – http://www.howstuffworks.com/led1.htm

Materials For each student team

Battery Mini light bulb (incandescent) Optional: LED bulb (need 2 batteries for LED) Piece of aluminum foil, 2” x 8” Household/standard light bulb (clear) Tape For each student Science notebook Pencil Facts of Light handout

For class Incandescent light bulb CFL light bulb LED light bulb 3 thermometers 3 table lamps 3 energy meters Overhead 1: Diagram of an Incandescent Light Bulb Overhead 2: How Incandescent, CFL, and LED Bulbs Work Overhead 3: Comparing Efficiency of Incandescent, CFL, and LED Overhead 4: Making a Homemade Flashlight Overhead 5: Making a Flashlight

Preparation Light bulb comparison: Set up three table lamps on a table at least 18”

apart; and about 12” from a wall. Put an incandescent, CFL, and LED bulb in each of the three lamps. Bulbs should be of equivalent wattage or lumens. Tape three thermometers on the wall in front of each table lamp. Plug an energy meter into each lamp.

Optional: Prepare materials for “Making a Homemade Flashlight” for

each team. Time 60 minutes

LESSON 7 Closed Circuits and Light Bulbs Nagele, et al. 2016 page 84

Procedure 1. Demonstration: Light Bulb Comparison

a. Tell students: “Lighting accounts for a large portion of the electricity used in the United States. In schools, around 20 percent of the electric bill is from lighting and about 10 percent of your parents’ electric bill for your home or apartment. In many homes we use incandescent light bulbs like this one (show the incandescent bulb in the lamp). This kind of bulb is very inefficient (wasteful) because 90 percent of the electricity that goes to the bulb is converted into heat energy instead of light energy. If we use an energy efficient compact fluorescent light (CFL) bulb instead (show the CFL bulb in the lamp), it would use 70 percent less electricity than an incandescent for the same amount of light because the electricity is converted to light and very little to heat energy. A third kind of light bulb called an LED, or light emitting diode is even more energy efficient than a CFL.”

b. Demonstration: Show students that the three lamps each have a

different kind of bulb. Explain that they will compare the energy efficiency of the three by measuring the energy lost to heat using thermometers. Show and explain how the energy meters work, and tell students you will also measure the following of each bulb using the meter: watts used to light each bulb, cost of electricity to light each bulb, and the amount of carbon dioxide produced to light each bulb (assuming electricity is produced through burning coal). Tell students they will record the results for each to compare the bulbs for themselves.

c. Ask a volunteer to come up and read the temperature on the

thermometers. Have students record the beginning temperature and energy usage. Ask the volunteer to turn on the three lamps, make sure they’re facing the thermometers and are equidistant from the wall. Tell students you will leave the lamps on during the class period and then check the thermometers’ temperatures and energy meters a little later.

2. Demonstration: How a light bulb works

a. Give each team of students a clear incandescent bulb and review the parts of the bulb (overhead 1).

b. Let students know that the filament is extremely thin, long and

made of tungsten metal. Ask them to guess: In a typical 60 watt light bulb, how long is the tungsten filament? Answer: about 6.5 feet! The tungsten is arranged in a double coil in order to fit it all

LESSON 7 Closed Circuits and Light Bulbs Nagele, et al. 2016 page 85

in a small space. The filament is wound up to make one coil, and then this coil is wound to make a larger coil. Tungsten is used in light bulbs because it is an ideal filament material that does not melt when heated to extreme temperatures! Most metals will melt before reaching such extreme temperatures – the vibration will break apart the rigid structural bonds between atoms so that the material becomes a liquid. But tungsten has an abnormally high melting temperature so it will remain entire and emit light.

The filament in a light bulb is housed in a sealed, oxygen-free

chamber to prevent combustion. Argon, an inert gas, is typically used to fill light bulbs.

c. Show on Overhead 1 how electricity moves through one wire

from the side of the light bulb to the filament and then down the other wire and out the bottom of the light bulb. Emphasize this pathway (electricity travels in side of bulb and out bottom of bulb) as students will need to know this information in order to successfully build a homemade flashlight in the next investigation.

d. Show Overhead 2 and briefly explain how CFL and LED bulbs work. c. Return to complete the demonstration of the energy efficiency of

the three different bulbs. Have three volunteers, one for each bulb, read the thermometer and energy meter for their bulb. Ask students to record and compare in their teams.

d. Start a class discussion comparing the results, and asking students

to draw conclusion on the energy efficiency of the bulbs based on the results.

e. Distribute the handout: “Facts of Light”. Compare the information

provided and complete the math regarding the incandescent vs. CFL vs. LED bulbs using the handout and Overhead #3.

f. You can continue discussion with students comparing their results

to the information from overhead 3 and the handout: Facts of Light. Or you can see Graffiti activity for F and G of this lesson. See graphic on pages 88-89 of this lesson.

For example: “So, it would appear that it is cheaper to buy nine incandescent

bulbs, but are there other costs?” Possible answers: You would need to make nine trips to the store; costs are in time and gas.

LESSON 7 Closed Circuits and Light Bulbs Nagele, et al. 2016 page 86

You would have to dispose of nine bulbs that would sit in landfills forever. Resources used to make the nine bulbs would not have needed to be mined from the earth; those resources could have been used to make other products if we had instead chosen to buy one CFL. However, CFLs contain mercury, so this is why we are moving to LED bulbs.

2013, The NEED Project, www.NEED.org

g. Have students draw conclusions from the demonstration and ask

them why would people use incandescent bulbs when CFLs and LEDs are available? There are three reasons: lack of education about CFLs/LEDs, the high initial cost of CLFs/LEDs compared to incandescent bulbs, and consumer buying habits. Many people have never heard of CFLs or LEDs and few know that using CFLs/LEDs can save so much money and electricity. Many people see the price tag and they are getting a great bargain when they can buy 10 incandescent bulbs for the price of one CFL. They don’t understand that they can reduce their electric bills by 25 to 50 percent by converting to CFLs or know that CFLs last around 13 times longer than incandescent bulbs, and LEDs even longer yet.

EXTENSION ACTIVITY: Making a Homemade Flashlight

1. Making a Homemade Flashlight: Introduction to closed circuits. (Engineers problem solve) a. Tell Students to imagine they are walking in the woods late in the

day with a flashlight and the flashlight gets smashed on a rock when they accidentally drop it. They take the flashlight apart and find the light bulb and the batteries are okay, but the case has been destroyed. Night is fast approaching. Their challenge is to think like an engineer and design a way to light the bulb using the

LESSON 7 Closed Circuits and Light Bulbs Nagele, et al. 2016 page 87

batteries, a piece of aluminum foil, and tape they found in their backpacks.

b. Remind them that an engineer is part scientist and part artist. An engineer solves problems by using his/her science knowledge to draw and test possible solutions to the problem.

c. As engineers they will need to use their new knowledge about

circuits, batteries, and electricity to solve this problem of the broken flashlight, but first they need one more piece of scientific information.

d. Remind students of Overhead 1, a diagram of a light bulb and how

electricity moves up one wire to the filament (source of light and heat) and then down the other wire.

e. Remind students the three things needed for a successful closed

circuit (Overhead 4): • Electrical source (in this case, the battery) • A path for the electrons to flow (aluminum foil and light bulb) • Something for the electrons to do/power (the load) Have students record in their notebooks.

f. Ask each team to select a recorder, have the recorder draw a

picture of their team’s idea for lighting the bulb in their science notebook. Remind the recorder to label the parts: battery (electricity source), light bulb (work load), and aluminum foil (pathway).

g. Once their diagrams are drawn by the recorder, have the materials supplier collect the items needed from their imaginary backpack: tape, aluminum foil, battery, and light bulb.

First light bulb

"Bright Lights." 4-H Electric Series. Vol. 1. [Washington, D.C.]: National 4-H Cooperative Curriculum System, 2002. 11. Print.

LESSON 7 Closed Circuits and Light Bulbs Nagele, et al. 2016 page 88

h. Have each team with the builder as their lead construct their light source. Allow them to figure out the following on their own with little facilitation: • Cut the aluminum foil into a strip about 2” x 8” • Fold the foil over and over along the long edge, until you have

a piece that is still six inches long, but only ¼ inch wide. • Touch one end of the battery to the bottom end of the bulb,

and then connect and tape the side of the bulb to the strip of aluminum foil.

• Connect and tape the strip of foil to the other end of the battery.

i. Check with students to see if their design was successful; facilitate where needed.

j. Have students revise their design as necessary and add arrows to show the path that electrons flow.

k. Ask students what they think will happen if the bulb is placed on

top of the foil with each end of the foil taped to the terminals of the batteries. Have them independently draw and write their answer in their journal before testing.

l. Ask students, “Do you think we could use a wire instead of

aluminum foil to make a closed circuit to light the bulb?” Have students try. You may also give students the opportunity to try an LED bulb.

"Bright Lights." 4-H Electric Series. Vol. 1. [Washington, D.C.]: National 4-H Cooperative Curriculum System, 2002. 11. Print.

LESSON 7 Closed Circuits and Light Bulbs Nagele, et al. 2016 page 89

m. Using Overhead 5 “Making a Flashlight”, determine students’ understanding of a closed circuit.

Graffiti During the Graffiti strategy, students brainstorm ideas and record them on large sheets of chart paper. This is a creative way to collect thoughts from all or most of the students in the classroom. Steps 1. Place students in groups of three or four. 2. Provide each group with a large piece of paper divided into three or four sections, with a topic written in the middle. The topic can be the same or different for all groups. In this case depending on the size of your class, you may have two sheets for each type of light bulb to spread out activity. 3. Give students two-five minutes to think, talk, refer to their notes and record their ideas on their paper. 4. Have them stop writing, standup, and move as a group to a different piece of paper with a different type of light bulb on it. 5. All of the groups continue the above process until each group has contributed to every piece of paper. 6. Bring the whole class together to review everyone's contributions and to identify patterns and categories in what has been written. Example…Each Circle will have in it a different type of light bulb.

LESSON 7 Closed Circuits and Light Bulbs Nagele, et al. 2016 page 90

One quadrant can answer: is it cheaper to buy incandescent bulbs, or are there other costs? Possible answers: More trips to the store; costs are in time and gas. You would have to dispose of more bulbs that would sit in landfills forever. Resources used to make these bulbs would not have needed to be mined from the earth; those resources could have been used to make other products if we had instead chosen to buy one CFL. However, CFLs contain mercury, so this is why we are moving to LED bulbs. Second quadrant can answer: why would people use incandescent bulbs when CFLs and LEDs are available? Some reasons: lack of education about CFLs/LEDs, the high initial cost of CLFs/LEDs compared to incandescent bulbs, and consumer buying habits. Third quadrant can answer: what type of energy efficiency does this type of bulb have? And what evidence can you cite for your answers? Hint: think back to your demonstrations and your fact sheet. They don’t understand that they can reduce their electric bills by 25 to 50 percent by converting to CFLs or know that CFLs last around 13 times longer than incandescent bulbs and LEDs even longer yet. Fourth quadrant can answer: your educated opinion about using this type of light bulb and why you would or would not use it. You can have the team decide on its answer or have each student write their own answers.

Assessment Score “Facts of Light” handout and notations in students’ notebooks. Use the discussion from the Graffiti exercise to see if students are

expressing what they have learned.

LESSON 7 Closed Circuits and Light Bulbs Nagele, et al. 2016 page 91

RESOURCES: Short Videos that demonstrate energy This Energy 101 video explores the different lighting options available to consumers. http://energy.gov/energysaver/articles/lighting-choices-save-you-money When you're shopping for lightbulbs, compare lumens and use the Lighting Facts label to be sure you're getting the amount of light, or level of brightness, you want. http://energy.gov/public-services/homes/saving-electricity/lighting How a light bulb works 1:13min http://www.youtube.com/watch?v=YnMP1Uj2nz0 How modern light bulb works ..nice graphics and moves fast. Compliments lesson nicely. 2:57min http://www.youtube.com/watch?v=oCEKMEeZXug How light bulbs are made 5:17 http://www.sciencekids.co.nz/videos/engineering/lightbulbs.html EXTENSION ACTIVITIES Interactive art: CLOUD is a large-scale interactive sculpture created from 6,000 light bulbs (new and burnt out) by Canadian artists Caitlind r.c. Brown & Wayne Garrett. The piece utilizes everyday domestic light bulbs and pull strings, re-imagining their potential to create wonder and inspire collaboration. http://vimeo.com/49748983 BUILD A LIGHT BULB - CIRCUIT SCIENCE Create a battery-powered light bulb from household items w/a video also. http://www.stevespanglerscience.com/lab/experiments/build-a-light-bulb-circuit-science OTHER RESOURCES Comparison of types of light bulbs, similar but more color. http://www.designrecycleinc.com/led%20comp%20chart.html FAQ on purchasing lights http://energy.gov/energysaver/articles/frequently-asked-questions-lighting-choices-save-you-money Website with more than you ever want to know about types of lighting http://energy.gov/public-services/homes/saving-electricity/lighting