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MATHEMATICSMATHEMATICSMATHEMATICSMATHEMATICSMATHEMATICS

WATT’S UP WITH CURRENT ELECTRICITY?WATT’S UP WITH CURRENT ELECTRICITY?WATT’S UP WITH CURRENT ELECTRICITY?WATT’S UP WITH CURRENT ELECTRICITY?WATT’S UP WITH CURRENT ELECTRICITY? GRADES 9- 10JANET CUNDIFF

TIME ALLOTMENT:TIME ALLOTMENT:TIME ALLOTMENT:TIME ALLOTMENT:TIME ALLOTMENT:Five 50-minute class periods.

OVERVIEW:OVERVIEW:OVERVIEW:OVERVIEW:OVERVIEW:Georg Simon Ohm, son of a self-taught man

was the first person to devise a mathematicalrelationship among the three units of electricalmeasurement, volt, ohm, and amp. Although earlypublications began reporting his work in the 1820’s,he was not well received by the physicists of thetime. His work was eventually recognized by theRoyal Society with its award of the Copley Medalin 1841.

Ohm’s Law deals with the relationship betweenvoltage and current in an ideal conductor. Thisrelationship states that: “The potential difference(voltage) across an ideal conductor is proportionalto the current through it.”

This, simply put, means that experimentationwill find that as voltage is increased, current willalso increase. If voltage is held constant andresistance increases, amps (current) will decrease.

In this series of activities, students will be ledto make the same generalizations through onlineresearch, experimentation, and through a hands-on laboratory approach.

SUBJECT MATTER:SUBJECT MATTER:SUBJECT MATTER:SUBJECT MATTER:SUBJECT MATTER: Mathematics,Physical Science

LEARNING OBJECTIVES:LEARNING OBJECTIVES:LEARNING OBJECTIVES:LEARNING OBJECTIVES:LEARNING OBJECTIVES:The student will:

• Define the terms volt, amp, ohm, and watt.• Explain the relationship among these

units of electricity.• Use a multimeter to measure volts,

amps, and ohms.• Calculate each of these units .• Illustrate the calculations through a

series of experiments.• Analyze resulting data to develop

generalizations relating these terms.

STANDARDS:STANDARDS:STANDARDS:STANDARDS:STANDARDS:National Science Education StandardsProgram Standard C: The science program

should be coordinated with themathematics program to enhance studentuse and understanding of mathematics inthe study of science and to improvestudent understanding of mathematics.

Louisiana Science Content Standardshttp://www.louisianaschools.net/conn/standards1.phpScience-InquirySI-H-A6: communicating and defending a

scientific argument; (1, 3, 4)S1-H-A7: utilizing science safety procedures

during scientific investigations (3, 5)Physical SciencePS-H-E1: recognizing the characteristics and

relative strengths of the forces of nature(gravitational, electrical, magnetic,nuclear); (4, 5)

PS-H-G2: analyzing the relationship andinteraction of magnetic and electrical fieldsand the forces they produce; (1, 2, 3, 4)

Math-AlgebraA-3-H: using tables and graphs as tools to

interpret algebraic expressions,equations, and inequalities; (1, 3)

A-4-H: solving algebraic equations andinequalities using a variety of techniqueswith the appropriate tools (e.g., hand-heldmanipulatives, graphing calculator,symbolic manipulator, or pencil andpaper) (2, 3)

Louisiana Mathematics Frameworkhttp://www.louisianaschools.net/lde/uploads/1646.pdfMath-MeasurementM-1-H: selecting and using appropriate units,

techniques, and tools to measurequantities in order to achieve specifieddegrees of precision, accuracy, and error(or tolerance) of measurements; (3)



MEDIA COMPONENTS:MEDIA COMPONENTS:MEDIA COMPONENTS:MEDIA COMPONENTS:MEDIA COMPONENTS:unitedstreaming™ Videos http://www.unitedstreaming.com/index.cfm

1. Electricity and Magnetism: Measuring and Using Electricity (13:43)2. Physics: A World in Motion: Ohm’s Law and Energy (29:00)

Web sites:Internet Guide to Electronics: Ohm’s Law Explainedhttp://webhome.idirect.com/~jadams/electronics/ohm.htm This site is written by a respected technical writer,Howard W. Sams, gives simple, illustrated explanations of somewhat abstract ideas on electrical topics.

This Learning Technologies Project from NASA gives schematic diagrams and a few practice problems topractice using Ohm’s Law. http://www.grc.nasa.gov/WWW/K-12/Sample_Projects/Ohms_Law/ohmslaw.html.

Molecular Expressions: Electricity and Magnetism Introduction was created by Michael W. Davidsonin cooperation with Florida State University. http://micro.magnet.fsu.edu/electromag/java/ohmslaw/It is an interactive site which demonstrates the relationship among the three variables we are studying:volts, ohms, and amps.

MATERIALS:MATERIALS:MATERIALS:MATERIALS:MATERIALS:Per Group

• One computer per group of 2 (recommended)• Lab supplies as indicated, per group:

o 2 one and a half volt dry cells and battery holderso Assorted wireso 2 one and a half volt bulbso 2 socketso Switch (optional)o Multimeter

Per Student• Student Sheets 1, 2, 3 (attached)

Per Class• Inspiration® software or other graphic organizer technique• Presentation station

PREP FOR TEACHER:PREP FOR TEACHER:PREP FOR TEACHER:PREP FOR TEACHER:PREP FOR TEACHER:1. Gather supplies as indicated.2. Conduct experiments as indicated to determine baseline of approximate values for specific

equipment used.3. Copy student sheets.4. Test all Web sites 24 hours prior to day of use.5. Download streaming video to school server or teacher computer for easy accessibility.6. Preview unitedstreaming™ videos. Review Focus for Media Interaction: a specific task to

complete and/or information to identify during of after viewing of video segments, Web site, or othermultimedia elements.

7. Divide students into teams/groups (2-3 recommended).



INTRODUCTORY ACTIVITY:INTRODUCTORY ACTIVITY:INTRODUCTORY ACTIVITY:INTRODUCTORY ACTIVITY:INTRODUCTORY ACTIVITY:Setting the Stage

1. Pre-viewing - Review Focus for Media Interaction:• In small groups, discuss, take notes, and report out: How would students’ lives be different if

they had to live a day without electricity? That is, how would it change their daily activities?What would be impossible to do without it? How is life improved by the use of it?

• Have you ever seen someone measuring electricity? What equipment were they using? Whatunit is used for measuring the light bulb? ...appliances? ...house current?

2. View unitedstreaming™ Videos’ Physics: A World in Motion: Ohm’s Law and Energy -Program Overview (01:04) http://www.unitedstreaming.com/index.cfm

3. What is this series of videos going to describe for us?

LEARNING ACTIVITIES:LEARNING ACTIVITIES:LEARNING ACTIVITIES:LEARNING ACTIVITIES:LEARNING ACTIVITIES:1. Distribute chart Electricity: Units of Measurements. (See student sheet 1 and teacher notes in

Appendix.) Assign students to work with partners to fill in the chart while watching video clips, asdesignated below:• Watch Electricity and Magnetism: Measuring and Using Electricity - Measuring

Electricity (06:30). http://www.unitedstreaming.com/index.cfm• Focus for Media Interaction: Record a definition or explanation of watts, amps, and volts in the

chart. List the formula for finding each one. Discuss with the students, the flowing wateranalogy for amps and volts.

• Watch Physics: A World in Motion: Ohm’s Law and Energy – Resistance (04:12).http://www.unitedstreaming.com/index.cfm

• Focus for Media Interaction: Record a definition or explanation and a formula for findingresistance. Add an explanation of the flowing water analogy as it relates to resistance. (Turningthe nozzle on the hose up or down is adding resistance to the flow of water, similar to addingresistance to the flow of electrons in certain materials.

2. Teacher’s note on Ohm’s Law: An easy to use and understand circle diagram to convert the Ohm’s Lawformula is found on the following Web site. http://webhome.idirect.com/~jadams/electronics/ohm.htmDemonstrate the process using the practice problems on http://www.grc.nasa.gov/WWW/K-12/Sample_Projects/Ohms_Law/ohmslaw.html.Other problems may be assigned as needed.

3. Using the interactive circuit found at the following website, create a graph showing the relationshipbetween resistance and amps. Select a static voltage, adjust the resistance, and record theresulting change in amperage. Record data on Student Handout 2 and graph the results.http://micro.magnet.fsu.edu/electromag/java/ohmslaw/

4. Post viewing: Discuss the analogy of water flowing with the units of electrical measurement.5. During reporting process, use graphic organizer (such as Inspiration® software with projector) or

white board to display student answers to pre/post viewing questions. Divide responses intocategories as indicated by the questions above.



CULMINATING ACTIVITY:CULMINATING ACTIVITY:CULMINATING ACTIVITY:CULMINATING ACTIVITY:CULMINATING ACTIVITY:1. Lab work: Using the set ups as indicated on Student Sheet 3 and the data table below, calculate

the missing variable by using Ohm’s Law.

Data Table

Set up Voltage Measure Calculate Ohms Amps

1 cell, 1 bulb 1 ½ v

2 cells in a series (1 1/2v each), 3 v Total of both2 bulbs in series

2 cells (this time in parallel) 1 ½ vand 1 bulb

2 cells (also in parallel) 1 ½ v Each oneand 2 bulbs in a series

2. Discuss results. Draw conclusions from data. Summarize unit content.

CROSS-CURRICULAR EXTENSIONS:CROSS-CURRICULAR EXTENSIONS:CROSS-CURRICULAR EXTENSIONS:CROSS-CURRICULAR EXTENSIONS:CROSS-CURRICULAR EXTENSIONS:LANGUAGE ARTS:

• Explain the relationship between voltage, ohms, and amps in a circuit. How would a larger bulbin a circuit affect the amperage of the circuit? Explain your answer.

• Research Georg Simon Ohm, son of a self-taught man, who first established the mathematicalrelationship among volts, ohms, and amps.

TECHNOLOGY:• Many Web sites are used as part of these activities, involving research and interactive animations.

Graphing and data tables could also be completed on the computer by the students if desired.

COMMUNITY CONNECTIONS:COMMUNITY CONNECTIONS:COMMUNITY CONNECTIONS:COMMUNITY CONNECTIONS:COMMUNITY CONNECTIONS:• Find 5 appliances in your home that are labeled with amps. Remember that the voltage applied for most

appliances is the total house voltage, 120 volts. Calculate the resistance provided by each appliance.• How is it possible to use electric fences to stop animals from leaving their confinements? What keeps the

electricity from seriously harming the animals? What causes the harm, voltage, amps, or a combination?• What voltage and/or amps is considered safe to humans or what safety concerns should homeowners be

aware in doing electrical repairs around the house?



STUDENT MATERIALS:STUDENT MATERIALS:STUDENT MATERIALS:STUDENT MATERIALS:STUDENT MATERIALS:• Appendix - STUDENT SHEET 1: Electricity: Units of Measurement• Appendix - STUDENT SHEET 2: Measuring Electricity and Ohm’s Law• Appendix - STUDENT SHEET 3: LAB: Measuring Electricity and Ohm’s Law• Supplies per lab group:

o 2 one and a half volt dry cells and battery holderso Assorted wireso 2 one and a half volt bulbso 2 socketso Switch (optional)o Multimeter



Electricity: Units of MeasurementStudent Sheet 1

Unit Definition Water Analogy Formula

W WATTS ———

I AMPS *

R OHMS *

E VOLTS(electromotive

force or EMF)

*

*Ohm’s Law demonstrates the relationship between the three units of measurement: volts, ohms, and amps.



Electricity: Units of MeasurementStudent Sheet 1

Unit Definition Water Analogy Formula

W WATTS ———

I AMPS *

R OHMS *

E VOLTS(electromotive

force or EMF)

*

*Ohm’s Law demonstrates the relationship between the three units of measurement: volts, ohms, and amps.

Power or amountof work done

Rate of electronflow- quantity of

electrons passinga given point in a

unit of time

Opposition to theflow of electrons

Force or strengthpushing the

electrons throughthe wire

Amount of waterflowing through the

end of a hose; similarto the gallons of waterpassing through thenozzle in one minute

Tightening or looseninga nozzle on a hose

allowing less or morewater to pass throughthe end of the hose

Water pressure of thecity’s water supply

(Is it peak time with alarge demand on theresources, causing

low water pressure?)

Watts =volts X amps

Amps =volts/resistance

Resistance =volts/amps

Volts =amps X ohms



Measuring Electricity and Ohm’s LawStudent Sheet 2

1. Using the interactive circuit found at the following website, select approximately 110 volts, adjust theresistance as shown below, and record the resulting change in amperage in the data table.

http://micro.magnet.fsu.edu/electromag/java/ohmslaw/2. Calculate the amps using Ohm’s Law and fill in the fourth column. How close are you to the answers

on the Web site? Show your work on the back of this sheet.Data Table

Voltage Resistance Actual results from website meter Your calculations of the AMPS 110 v 100 ohms 110 v 50,095 ohms 110 v 150,085 ohms 110 v 250,075 ohms 110 v 450,055 ohms

3. Create a graph showing the relationship between resistance and amps shown in the table above.

Amps

Ohms

4. What conclusions can you draw from the data in the graph? What is the relationship between ampsand resistance? Why is this true?



LAB: Measuring Electricity and Ohm’s LawStudent Sheet 3

1. Conduct the experiment as indicated by the set-ups in the table.2. Determine the resistance of the bulb/s you are using by measuring them with the multimeter. Include

the measurements in the resistance column in the table.3. Calculate the missing amps by using Ohm’s Law. Show your work on the back of this sheet.

Note: Check the bulbs with the 1 ½ v. battery before starting, to ensure that the bulb is functional. Some set-ups may not light up, but the meter will still indicate that current is flowing.

Data Table

Set up Voltage Measure Calculate Ohms Amps

1 cell, 1 bulb 1 ½ v

2 cells in a series (1 1/2v each), 3 v Total of both2 bulbs in series

2 cells (this time in parallel) 1 ½ vand 1 bulb

2 cells (also in parallel) 1 ½ v Each oneand 2 bulbs in a series

3. What conclusions can you draw from the data in the data table?How does the set up of the cells affect the amps?How does the set-up of the cells affect the brightness of the bulbs?Why didn’t some of the bulbs light up?

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