Teacher Notes for Electric Circuits

Lesson Plans || Learning Outcomes and Activities || Teacher Notes || Labs

 

Unit Plans

We estimate this to be a 15-day unit if you address all the Learning Outcomes. An additional day should be added for an exam. There are three primary goals for the unit:
 

1. To understand the nature of charge flow in electric circuits, including the requirement of a closed conducting loop and the presence of an energy source to maintain an electric potential difference across the two ends of the circuit.
2. To understand basic circuit concepts such as current, voltage, resistance, energy, and power and the mathematical relationship between voltage, current, and resistance.
3. To analyze both series and parallel circuits in order to determine such quantities as the voltage drop across and current in individual resistors and the battery.

Our Lesson Plans and Pacing Guide allocate eight days to an understanding of basic circuit concepts and quantities. The remaining seven days are devoted to understanding of the concepts and mathematics of series and parallel circuits (and a day for review).


 

The Calculator Pad (a.k.a., CalcPad)

With the CalcPad section of our website, you will likely never have a shortage of problems to draw from. The Electric Circuits section of our Calculator Pad includes 15 problem sets with well over 100 problems. We used this bank of problems to create three custom CalcPad problem sets for the Conceptual Physics course. The second and third problem sets included existing problems that were cloned and modified to be more appropriate for this level of a course. If you need more problems or are looking for problems with less scaffolding, you will find them among these 15 problem sets. With a Task Tracker subscription and our directions and video walk-throughs, you can even create your own custom problem sets or edit one of ours. 


 

DC Circuit Builder

One of the simulations in the Physics Interactives section is DC Circuit Builder. This simulation provides the user a virtual electronic circuit board. Add resistors, light bulbs, wires and ammeters to build a circuit. Explore Ohm's law. Compare and contrast series, parallel, and combination circuits. Use a voltmeter to measure voltage drops. We have created five different student activities for use with this simulation and four interactive Concept Checkers. Our Lesson Plans rely upon four of these activities; each has an accompanying Concept Checker.


 

Labs

We have proposed six labs for this unit. Since four of these do not have any Teacher's Guides available, we will supply some notes here. Additional details are on our Lab Page for this unit. We are big fans of the CASTLE (Capacitor-Aided Strategies for Teaching and Learning about Electricity) curriculum. Supplies can be purchased from Pasco Scientific. Labs 1 - 5 are variants from some of the activities found in the CASTLE Student Guide (free download).

Lab 1: Lab 1 is identical to a lab that we have used for our other courses. We have provided a link to the Teachers Guide on our Lab page.

Lab 2: Lab 2 requires the use of a magnetic compass, a battery pack with up to four cells, three identical bulbs and accompanying sockets, and sufficient wires to make the circuit connections. Students use the direction of compass deflection under varying wires to determine the relative direction of charge flow through each wire. They use the amount of deflection to determine the relative rate of charge flow in each wire. Specifically, they are attempting to determine if charge flow rates increase or decrease with proximity to or distance from a battery terminal. And they are attempting to determine if charge flows out of each end of the battery in opposite directions towards the bulbs or if charge moves in one direction around the circuit. Then starting with a 1 cell, 2 bulb series circuit, students can add cells and observe the effect of increasing number of cells upon the brightness of bulbs (and thus, the current). And starting with a 2 cell, 1 bulb circuit, students can add bulbs in series and observe the effect of increasing number of bulbs upon the brightness of bulbs (and thus, the current). 

Lab 3: Lab 3 requires the use of a battery pack with three cells, a socket with a light bulb, additional bulb not in a socket, several wires, and a household incandescent light bulb with the glass bulb safely removed to allow testing of the bulb parts. Students build a conductor testing circuit with two free leads that can be touched to conductors and insulators to observe their ability to complete the circuit. They then use the testing circuit to touch varying parts of a free bulb (not in socket), touching bottom tip, the ribbed side (opposite parts), the black insulator wedged between the ribbed side and the bottom tip, and the glass bulb. Students record observations in an attempt to determine how charge gets through a light bulb to light the light bulb. Students also use the household bulb to determine how it conducts. With the glass removed, they can touch the leads to the filaments and filament supports and observe what conducts. Finally, they can repeat by testing the lab sockets provided with the electricity kits.

Lab 4: Lab 4 requires the use of a battery pack with three cells, three identical bulbs and accompanying sockets, a carbon resistor, sufficient wires to make the circuit connections, several coffee stirrers, several straws, a milkshake straw, and scotch tape. Starting with a 3 cell, 1 bulb circuit, students can a second and third bulb in series and observe the effect of increasing number of bulbs upon the brightness of bulbs. They then add a carbon resistor to a 3 cell, 1 bulb circuit and observe the effect on bulb brightness. They reason that a bulb is like a resistor due to its affect upon bulb brightness and current. Students then use an air flow model. For hygiene and experimental control purposes, the same student in a lab group will inhale fully and then exhale through sealed lips on a coffee stirrer, a straw, and a milkshake straw in three consecutive trials. They measure the time for air to flow from filled lungs through the conduit. They then repeat the timing for four straws (or stirrers) sealed end-to-end by scotch tape (series-connected) and through several straws (or stirrers) arranged side-by-side (parallel-connected).

Lab 5: Lab 5 requires the use of four sockets, two battery packs with three cells each, two bulbs of the same type (we call it bulb C) and two bulbs of different type - bulbs A and B. It is permitted that Bulb C be identical to bulb A. Students build two contrasting two bulb circuits. In Circuit 1, Bulb A is with Bulb C. In Circuit 2, Bulb B is with Bulb C. Bulb C is the control. It's brightness is greatest when it is with the bulb that has the least resistance. Students make observations of Bulb C and use the observations to conclude which bulb has the greatest resistance. They then use a compound microscope to observe the relative diameter of the Bulb A and B filaments and filament supports. When combined with what was learned in Lab 4, they can provide an explanation of why one bulb has a greater resistance than the other bulb.

Lab 6: Lab 6 is identical to a lab that we have used for our other courses. We have provided a link to the Teachers Guide on our Lab page.

 

And More Labs

We did not include any labs on series and parallel circuit analyses on our Lesson Plans. Instead we relied on our DC Circuit Builder tool. We don't always feel good about replacing hands-on experiences with simulations. But with this level of student, it seemed like the more appropriate optoin. Teachers may want to be bold and give the hands-on labs a try. Two labs we have used in our other courses are hands-on and within the reach of on-level and honors-level students are described below: 

 

Lab 7 - Comparing Voltage Drops and Currents in Series

Question:
How do the voltage drops across the three resistors of a series circuit compare to each other? Are these voltage drops different for different resistors? How do the voltage drops compare to the voltage gain in the battery? How do the current values in the individual resistors compare to each other? Are these currents affected by the resistance of the resistors? How do the current values compare to the current at the battery location? For any individual resistor, how is the voltage drop, current and resistance related? How can all these comparisons be expressed using mathematical equations?

Purpose:
To compare current values at the three resistor locations of a series circuit and to compare voltage drops across the three resistors of a series circuit and the voltage gain across the battery.

A complete lab write-up includes a Title, a Purpose, a Data section, and a Conclusion/Discussion of Results. The Data section should include a schematic of a three-resistor series circuit with labeled resistors. The resistance values should be indicated on the diagram. Ammeter locations should be indicated on the diagram as well. Measurements of Delta V₁, Delta V₂, and Delta V₃ should be indicated in a table or on the diagram. Measurements of I₁, I₂, and I₃ should be indicated in a table or on the diagram. The Conclusion/Discussion should identify equations relating the voltage drops for each resistor to the current at the resistor location and the resistance value. The voltage drops for the resistors should be compared to the voltage gain in the battery. Conceptual ideas should be extracted from the data and referenced to the data. Equations should be stated. An error analysis should be performed and percent difference values calculated.

View: Teacher's Guide

 

Lab 8 - Comparing Voltage Drops and Currents in Parallel

Question:
How do the voltage drops across the three resistors of a parallel circuit compare to each other? Are these voltage drops different for different resistors? How do the voltage drops compare to the voltage gain in the battery? How do the current values in the individual branches compare to each other? Are these currents affected by the resistance of the branches? How do the current values compare to the current at the battery location? For any individual resistor, how are the voltage drop, current and resistance related? How can all these comparisons be expressed using mathematical equations?

Purpose:
To compare voltage drops across the three resistors of a parallel circuit and to compare current values at the three resistor locations and outside of the branches of a parallel circuit.

A complete lab write-up includes a Title, a Purpose, a Data section, and a Conclusion/Discussion of Results. The Data section should include a schematic of a three-resistor parallel circuit. The resistance values should be indicated on the diagram. Ammeter locations should be indicated on the diagram as well. Measurements of Delta V₁, Delta V₂, and Delta V₃ should be indicated in a table or on the diagram. Measurements of I₁, I₂, and I₃ should be indicated in a table or on the diagram. The Conclusion/Discussion should identify equations relating the branch currents to the voltage drop and resistance values for those branches and to relate the branch currents to the total current in the circuit. Conceptual ideas should be extracted from the data and referenced to the data. Equations should be stated. An error analysis should be performed and percent difference values calculated.

View: Teacher's Guide

 

Electrical Power

We pretty much relied on everything we have in creating our Lesson Plans. There are several resources that we did not list in our Lesson Plans but we included them in our Day 15 Review day. One topic that we did not include in our outcomes or in our Lesson Plans is the topic of electrical power. If you would like to add the topic back end, the following resources would be helpful"
 

1. Physics Classroom Tutorial: Lesson 2, Part d on Power - Putting Charges to Work
    
2. Physics Classroom Tutorial: Lesson 3, Part d on Electric Power Revisited
    
3. Video Tutorial: Electric Power
    
4. Minds On Physics: Mission EC6: P, V, I, R, and Cost Calculations
    
5. Concept Builder: Case Studies - Electric Power
    
6. Calculator Pad, Electric Circuits, Problem Sets EC5 - EC8
    

 

Teacher Presentation Pack

Here we go again ... throwing in an advertisement in the middle of a Teacher Notes page. But while we are advertising a for-sale item, we are also promoting an item that will potentially save the buyer a load of time. It's our Teacher Presentation Pack. It's a well-worth-the-cost tool for any Physics teacher. But for the early-career and cross-over Physics teacher, it's a life saver ... or at least a time saver. It includes a large collection of Slide Decks, Lesson Notes, animations, and graphics for use in your classroom. Once downloaded, you can modify and customize the Slide Decks as needed. You can upload them to your Google Drive and make them available to students. Use the slides as graphic organizers as you prepare students for a Concept Builder or quiz or test. Or use the Slide Decks to organize your presentation of material. Use the content as is. And customize it to make it your own. Learn more.


 

Also Available ...

Physics teachers may find the following for-sale tools to be useful supplements to our Lesson Plan and Pacing Guide section:

 

1. Task Tracker Subscription (annual purchase)
   A subscription allows teachers to set up classes, add students, customize online assignments, view student progress/scores, and export student scores. Task Tracker accounts allow your students to begin assignments in class or at school and to finish them at home. View our Seat and Cost Calculator for pricing details.
    
2. The Solutions Guide
   We publish a free curriculum with >200 ready-to-use Think Sheets for developing physics concepts. The Solutions Guide is a download containing the source documents, PDFs of source documents, and answers/solutions in MS Word and PDF format. An expanded license agreement is included with the purchase. (Cost: $25 download)
    
3. Teacher Presentation Pack
   This is a large collection of downloadable content packed with nearly 190 Microsoft PowerPoint slide decks, the corresponding Lesson Notes (as PDF and fully-modifiable MS Word format), about 170 animations (in .gif, .png, and .mp4 file formats), a countless number of ready-to-use images (including the original source documents that would allow for easy modification of those images), and a license that allows teachers to modify and use all the content with their classes on password-protected sites (such as course management systems).  (Cost: $40 download)
    
4. Question Bank
   We distribute a Question Bank that includes more than 9300 questions neatly organized according to topic. The Question Bank is the perfect tool for busy teachers or new teachers. Even if you don't use the website with your classes, the Question Bank will assist you in quickly putting together quizzes, tests and other documents with high-quality questions that target student's conceptions of physics principles. And if you do use The Physics Classroom website, the Question Bank is the perfect complement to the materials found at the website. (Cost: $25 download)