Electromagnetism: Ohm's Law
Central Concept : Stationary and moving charged particles result in the phenomena known as electricity and magnetism
Lesson Plan
State Standards:
Learning Standard: Introductory Physics, High School
5.2 Develop qualitative and quantitative understandings of current, voltage, resistance, and the connections among them (Ohm's law).
Essential Question:
How do you know that the relationship between voltage, current and resistance is determined by Ohm's law?
Lesson Question:
What determines the amount of current that flows in an electric circuit?
Introduction:
The electric tools and appliances you use daily transfer electric energy to another form of energy. The electric circuit they belong to obeys Ohm's law. In this lesson you will be measuring the current in an electric circuit and the voltage (potential difference) across resistors (light bulbs) placed in series. After you discover the relationship between current, voltage and resistance you will be able to explain Ohm's law and solve problems involving electric circuits. Subsequent lessons will apply this investigation to resistors in parallel.
Task:
Your goal is to collect data on current, voltage and resistance in an electric circuit. You will create a graph of voltage verses current from the data and determine the slope line of best fit. An online excel spreadsheet will be used to compile the measurements of the whole class and will also aid in creating graphs. Data will also be obtained at home or in class using a PhET electric circuit simulation which will be added to existing measurements.
Lesson Experiences:
You will be grouped together in 23 students per group.
Begin your investigation by doing the
Ohm's Law Activity 1.
Ohm's Law Activity 1
You will be creating a simple circuit using a battery connected to a light bulb and knife switch.
You will use an ammeter and voltmeter to measure the current in the circuit and potential difference (voltage drop) across the battery and light bulb. Readings will be recorded and analyzed.
The number of batteries and light bulbs will be varied and data recorded.
Procedure:
 Work in groups of 23
 Arrange one battery, knife switch, 1 light bulb and ammeter in series. (5 min.)
 Measure the potential difference (voltage) across the battery and light bulb using the voltmeter. (2 min.)
 Record the current in the circuit from the ammeter in the your data table. (1 min)
 Repeat the above steps using two bulbs and record results. (6 min)
 Use two batteries connected in series with one light bulb. (3 min)
 Finally add two light bulbs in series and record results. (3 min)
Sample Data Table
Leonard Martino Period 3 Date: 

Voltage drop 
Current Flowing 
Current Flowing 

1 Battery 

Light bulb #1 

Light bulb #2 

2 Batteries 

Light bulb #1 

Light bulb #2 
Place your data in the spreadsheet. ( Activity 1 Worksheet link)
After you obtain your results, discuss these misconceptions:
 Voltage is measured as the potential difference across two points in a circuit.
 Charge moves through a circuit.
Web 2.0 : homework: PhET electric circuit simulation
Your Objective: Construct a series circuit and measure the voltage drop across each resistor and the current before and after each resistor in the circuit.
Instructions:
 Click on the DC circuit simulation below.
 Construct a series circuit using 1 battery and 2 light bulbs.
 Measure the voltage across the battery using the voltmeter and record the result.
 Measure the voltage across each light bulb using the voltmeter and record the result.
 Measure the current in the wire before and after each light bulb using the noncontact ammeter or the ammeter that you connect directly into the circuit and record the result.
 Join 2 batteries in series to the circuit and repeat steps 25 above.
 Place your collected data in the spreadsheet using the link below.
 Answer the two questions below by clicking on the link.
Sample Data Table
Leonard Martino Period 3 Date: 

Voltage drop 
Current Flowing 
Current Flowing 

1 Battery 

Light bulb #1 

Light bulb #2 

2 Batteries 

Light bulb #1 

Light bulb #2 
Place your data in the spreadsheet . (Activity 1 Worksheet link)
 State two things that you observed about the voltage across the battery and the voltage drop across each light bulb in the two circuits.
 State two things you know about the current flowing in a series circuit.
Click on the link to place your answers to the questions above.
This activity may be started in class or outside of school.
Your Objective(s): Be able to:
 analyze the arrangement of electric components in a series circuit.
 connect a voltmeter and ammeter to various points in a series circuit and observe voltage and current.
 create a graph of voltage verses current and determine the line of best fit for the data.
 calculate the slope the line and relate it to resistance of the circuit.
Instructions:
Using the PhET electric circuit simulation, you will attach a battery, ammeter,light bulb and switch in series and connect a voltmeter across the light bulb.
Example diagram:
Sample Data Table
Leonard Martino Period 3 Date: 

Voltage drop 
Current Flowing 
Current Flowing 

1 Battery 

Light bulb #1 

Light bulb #2 

2 Batteries 

Light bulb #1 

Light bulb #2 
 You will then close the switch and record the current and voltage across the battery.
 Change the voltage of the the battery by right clicking in the image.
 Increase the voltage by 1 volt increments up to 10 volts.
 Record all your data in a data table
 Create a graph of Voltage verses Current
 Determine the line of best fit.
 Find the slope of the line.
 Write a brief description (one paragraph) on the relationship you found between voltage,current and resistance from Activity 1 and Activity 2
You may place your data in the spreadsheet located online or on your own spreadsheet ( Activity 2 Worksheet link).
Continue the investigation at home by using the PhET electric circuit simulation and add that data to the spreadsheet.
Note: The slope of the line is the total resistance . Ohm's law V = RI or V/I = R where R is the resistance which is constant (constant slope)
Discuss your results with the group in the next class. What have you discovered? How does this relate to Ohm's Law?
Conclusion:
Now that you have completed this lesson you are able to create a simple circuit and connect an ammeter and voltmeter properly in order to measure current and voltage. By collecting data on current and voltage drops at various places in the circuit, you have
developed a qualitative and quantitative understanding of current, voltage, resistance, and their relationship to each other. Using a spreadsheet to organize your data and graphing that data allowed you to see the relationship between current,voltage and resistance and verify Ohm's Law.
Assessments:
You will be assessed on the completion of both investigations and producing a data table and graph which includes a line of best fit and calculated slope. A brief explanation (one paragraph) on the relationship between voltage, current and resistance is also required.
Other assessments will include:
When we have finished the section on series circuits you will take an online quiz to better enable you to assess your own understanding of electric circuits. You may take the quiz as often as you need to so that you will become confident in your knowledge of this section of the text. Click on the link below and choose any of the quizzes labeled "series circuit."
ZOHO online quiz series circuit quiz
To help you review the entire chapter using Quizlet flashcards click here.
Resources:
Assessment Rubric for Activity 1 and Activity 2
You will be able to.... 
Strong 
Good 
Adequate 
Inadequate 
Weighting 
Arrange a simple circuit using a battery, 
circuit is correct and meters 
circuit is correct but 
circuit correct 
circuit not properly set up 

Create a simple circuit using computer simulation 
circuit is correct and meters 
circuit is correct but 
circuit correct 
circuit not properly set up 

Measure the voltage at various points in a circuit 
All voltage is measured 
Minor error in 
Few minor errors in 
Major errors in 

Organize data collected using Excel spreadsheet 
data is well organized and easily 
data is organized but 
data organized but 
Excel not used 

Create a Mass verses Volume graph of data using 
Graph is correct and 
Graph is correct with 
Graph is correct but 
graph is not correct 

Describe quantitatively the relationship between 
Description is excellent 
Description is good 
Description is adequate but is clearly stated 
Description is not 

Explain Ohm's law and solve problems involving 
Explanation and all problems are correct 
Explanation is correct 
Explanation and/or 
Explanations and/or 
Resources:
Eisenkraft, Arthur. Active physics A ProjectBased Inquiry Approach . 3rd ed. New York: Herff Jones Company, 2010.
Zitzewitz, Paul. Physics Principles and Problems .Ohio: Glenco/McGraw Hill Companies.2009.
Resources:
http://phet.colorado.edu/
http://www.zoho.com/creator/
http://quizlet.com/mathandscience/
http://www.youtube.com/watch?v=tUCtCYtyns&feature=youtube
anmeter, voltmeter or multimeter, 2 D size batteries with holders, 2 miniature light bulbs with holders, connecting wires, knife switch
Worksheets:
voltage/current activity1 worksheet
series/circuit data activity2 worksheet
Worksheets also available on Google Docs.
Image credits:
"Circuit" by Mamun2a, from Wikimedia Commons
"Multimeter" by Neo139, from Wikimedia Commons
"Bombeta de llum" from Wikimedia Commons.